When connecting to an RDP or SSh session and it fails, the error message receivied is not very helpful for troubleshooting purposes. For example if an RDP sessions just returns "Failed", this does not mean anything. We then need to look in the log files to find out that the password or user account has a problem.
SSH is no different. An error returning saying it "cannot create session" is not very helpful. This could mean anything literally. I have found this message to mean anything from port 22 is a problem, to the account is a problem etc.