POST /oauth/token failing with error "The SSL connection could not be established..."

I'm getting an exception when calling

POST /oauth/token

Exception Type:

System.IO.IOException

The full error message is:

The SSL connection could not be established, see inner exception. Received an unexpected EOF or 0 bytes from the transport stream.

I am only getting this error in our QA environment. When running locally or Dev environment, it is working as expected. Both Dev / QA use the same Degreed ClientID / ClientSecrets. Both use https://betatest.degreed.com/oauth/token

Just need some pointers on common scenarios where this error is being thrown

Thank you