Running knife client list leads to Object cannot be found error


I am new to chef, and have almost completed installation of chefdk, this maybe a silly question but i am unable to understand where i am going wrong.
I tried looking on the web and it said it could be due to knife.rb file. I tried re-configuring file but it doesn’t seem to be working. I am adding my file details please let me know where i am going wrong.

og_level :info
log_location STDOUT
node_name 'ps’
client_key '/home/ps/chef-repo/.chef/ps.pem’
validation_client_name 'chef-validator’
validation_key '/home/ps/chef-repo/.chef/chef-validator.pem’
chef_server_url 'https://psvm:443
syntax_check_cache_path ‘/home/ps/chef-repo/.chef/syntax_check_cache’

Also nodename was generated by knife configure and i do not have /syntax_check_cache file in .chef folder

my .chef structure is –
ps@psvm:~/chef-repo/.chef$ ls
chef-validator.pem knife.rb ps.pem trusted_certs

Any help is greatly appreciated