Backend error: 500 internal server error, Failed to create starter-kit

With the help of AWS cloud formation template I launched chef automate, chef workstation and a node. Took RDP of chef workstation and tried to download starter-kit using chef-automate's https:///biscotti/setup. When I complete filling the required fields, it ultimately fails.

Here is my template file.

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template deploys the AWS Chef Automate Quick Start. ***NOTE*** You must subscribe to the Chef Automate AMI from the AWS Marketplace before you launch this template. See the deployment guide at http://aws.amazon.com/quickstart for details. This template creates Amazon EC2 instances and related resources. You will be billed for the AWS resources used if you create a stack from this template.",
    "Metadata": {
        "AWS::CloudFormation::Interface": {
            "ParameterGroups": [
                {
                    "Label": {
                        "default": "Network Configuration"
                    },
                    "Parameters": [
                        "AvailabilityZones",
                        "PublicSubnetCIDR",
                        "RemoteAdminCIDR",
                        "VPCCIDR"
                    ]
                },
                {
                    "Label": {
                        "default": "Chef Automate Configuration"
                    },
                    "Parameters": [
                        "AdminPassword",
                        "ChefAutomateInstanceType",
                        "ChefNodes",
                        "IncludeDemoInstances",
                        "KeyPairName"
                    ]
                },
                {
                    "Label": {
                        "default": "AWS Quick Start Configuration"
                    },
                    "Parameters": [
                        "QSS3BucketName",
                        "QSS3KeyPrefix"
                    ]
                }
            ],
            "ParameterLabels": {
                "AdminPassword": {
                    "default": "Administrator password."
                },
                "AvailabilityZones": {
                    "default": "Availability Zones"
                },
                "ChefAutomateInstanceType": {
                    "default": "Chef Automate Instance Type"
                },
                "IncludeDemoInstances": {
                    "default": "Enable and Launch Demo Instances."
                },
                "QSS3BucketName": {
                    "default": "Quick Start S3 Bucket Name"
                },
                "QSS3KeyPrefix": {
                    "default": "Quick Start S3 Key Prefix"
                },
                "PublicSubnetCIDR": {
                    "default": "Public Subnet CIDR"
                },
                "VPCCIDR": {
                    "default": "VPC CIDR"
                }
            }
        }
    },
    "Parameters": {
        "AdminPassword": {
            "Description": "Password for the 'chefadmin' account used to sign into the Chef Management Console",
            "Type": "String",
            "NoEcho": "True"
        },
        "AvailabilityZones": {
            "Description": "List of Availability Zones to use for the subnets in the VPC. Note: The logical order is preserved and only 2 AZs are used for this deployment.",
            "Type": "List<AWS::EC2::AvailabilityZone::Name>"
        },
        "ChefAutomateInstanceType": {
            "Default": "t2.xlarge",
            "AllowedValues": [
                "t2.xlarge",
                "m4.xlarge",
                "m4.2xlarge",
                "m4.4xlarge",
                "m4.10xlarge",
                "c4.large",
                "c4.xlarge",
                "c4.2xlarge",
                "c4.4xlarge",
                "c4.8xlarge"
            ],
            "ConstraintDescription": "Must contain valid instance type",
            "Description": "Type of EC2 instance for the Master instances",
            "Type": "String"
        },
        "ChefNodes": {
            "Description": "Select the number of nodes you want to support.",
            "Default": 1,
            "MinValue": 1,
            "MaxValue": 10,
            "Type": "Number",
            "ConstraintDescription": "Must be a number between 1 and 10."
        },
        "IncludeDemoInstances": {
            "Description": "Set this value to 'true' to include a Chef workstation and demo node. For Chef Automate only, set to 'false'",
            "AllowedValues": [
                "true",
                "false"
            ],
            "Type": "String",
            "Default": "false"
        },
        "KeyPairName": {
            "Description": "Public/private key pair",
            "Type": "AWS::EC2::KeyPair::KeyName"
        },
        "QSS3BucketName": {
            "AllowedPattern": "^[0-9a-zA-Z]+([0-9a-zA-Z-]*[0-9a-zA-Z])*$",
            "ConstraintDescription": "Quick Start bucket name can include numbers, lowercase letters, uppercase letters, and hyphens (-). It cannot start or end with a hyphen (-).",
            "Default": "aws-quickstart",
            "Description": "S3 bucket name for the Quick Start assets. Quick Start bucket name can include numbers, lowercase letters, uppercase letters, and hyphens (-). It cannot start or end with a hyphen (-).",
            "Type": "String"
        },
        "QSS3KeyPrefix": {
            "AllowedPattern": "^[0-9a-zA-Z-/]*$",
            "ConstraintDescription": "Quick Start key prefix can include numbers, lowercase letters, uppercase letters, hyphens (-), and forward slash (/).",
            "Default": "quickstart-chef-automate/",
            "Description": "S3 key prefix for the Quick Start assets. Quick Start key prefix can include numbers, lowercase letters, uppercase letters, hyphens (-), and forward slash (/).",
            "Type": "String"
        },
        "PublicSubnetCIDR": {
            "Description": "CIDR Block for the Public Subnet",
            "ConstraintDescription": "CIDR block parameter must be in the form x.x.x.x/16-28",
            "Type": "String",
            "Default": "10.0.128.0/20",
            "AllowedPattern": "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\\/(1[6-9]|2[0-8]))$"
        },
        "RemoteAdminCIDR": {
            "AllowedPattern": "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\\/([0-9]|[1-2][0-9]|3[0-2]))$",
            "ConstraintDescription": "CIDR block parameter must be in the form x.x.x.x/x",
            "Description": "Allowed CIDR block for external SSH access Note: a value of 0.0.0.0/0 will allow access from ANY ip address",
            "Type": "String"
        },
        "VPCCIDR": {
            "Description": "CIDR Block for the VPC",
            "Type": "String",
            "Default": "10.0.0.0/16",
            "AllowedPattern": "[a-zA-Z0-9]+\\..+"
        }
    },
    "Rules": {
        "CheckSupportedRegions": {
            "Assertions": [
                {
                    "Assert": {
                        "Fn::Not": [
                            {
                                "Fn::Contains": [
                                    [
                                        "eu-west-3"
                                    ],
                                    {
                                        "Ref": "AWS::Region"
                                    }
                                ]
                            }
                        ]
                    },
                    "AssertDescription": "Chef does not currently support the Paris region"
                }
            ]
        }
    },
    "Conditions": {
        "GovCloudCondition": {
            "Fn::Equals": [
                {
                    "Ref": "AWS::Region"
                },
                "us-gov-west-1"
            ]
        }
    },
    "Resources": {
        "VPCStack": {
            "Type": "AWS::CloudFormation::Stack",
            "Properties": {
                "TemplateURL": {
                    "Fn::Sub": [
                        "https://${QSS3BucketName}.${QSS3Region}.amazonaws.com/${QSS3KeyPrefix}submodules/quickstart-aws-vpc/templates/aws-vpc.template",
                        {
                            "QSS3Region": {
                                "Fn::If": [
                                    "GovCloudCondition",
                                    "s3-us-gov-west-1",
                                    "s3"
                                ]
                            }
                        }
                    ]
                },
                "Parameters": {
                    "AvailabilityZones": {
                        "Fn::Join": [
                            ",",
                            {
                                "Ref": "AvailabilityZones"
                            }
                        ]
                    },
                    "CreatePrivateSubnets": "false",
                    "KeyPairName": {
                        "Ref": "KeyPairName"
                    },
                    "PublicSubnet1CIDR": {
                        "Ref": "PublicSubnetCIDR"
                    },
                    "VPCCIDR": {
                        "Ref": "VPCCIDR"
                    }
                }
            }
        },
        "InstanceStack": {
            "Type": "AWS::CloudFormation::Stack",
            "Properties": {
                "TemplateURL": {
                    "Fn::Sub": [
                        "https://${QSS3BucketName}.${QSS3Region}.amazonaws.com/${QSS3KeyPrefix}templates/chef-automate.template",
                        {
                            "QSS3Region": {
                                "Fn::If": [
                                    "GovCloudCondition",
                                    "s3-us-gov-west-1",
                                    "s3"
                                ]
                            }
                        }
                    ]
                },
                "Parameters": {
                    "AdminPassword": {
                        "Ref": "AdminPassword"
                    },
                    "ChefNodes": {
                        "Ref": "ChefNodes"
                    },
                    "IncludeDemoInstances": {
                        "Ref": "IncludeDemoInstances"
                    },
                    "KeyPairName": {
                        "Ref": "KeyPairName"
                    },
                    "QSS3BucketName": {
                        "Ref": "QSS3BucketName"
                    },
                    "QSS3KeyPrefix": {
                        "Ref": "QSS3KeyPrefix"
                    },
                    "RemoteAdminCIDR": {
                        "Ref": "RemoteAdminCIDR"
                    },
                    "SubnetId": {
                        "Fn::GetAtt": [
                            "VPCStack",
                            "Outputs.PublicSubnet1ID"
                        ]
                    },
                    "VPC": {
                        "Fn::GetAtt": [
                            "VPCStack",
                            "Outputs.VPCID"
                        ]
                    },
                    "VPCCIDR": {
                        "Fn::GetAtt": [
                            "VPCStack",
                            "Outputs.VPCCIDR"
                        ]
                    }
                }
            }
        }
    }
}