Chef Inspec connection failure

I am trying to run the command 'inspec shell -t ssh://user-name@x.x.x.x:22 -i /C:\Users\folder.ssh\name.ppk --show-progress --reporter cli html2:RH_test_report.html

The connection times out with the below message

[SSH] connection failed, retrying in 1 seconds (#<Net::SSH::AuthenticationFailed: Authentication failed for user root@x.x.x.x)

I am able to log into server via putty using .ppk authentication.
I am also able to ping the server.

inspec I believe uses a normal pem file not ppk file like putty for windows.

I change the .ppk to .pem file and still get the same error message.