I have not been able to reproduce this issue. Are you having the issue when you are creating the credentials or afterwards?
If it is while you are creating the credentials, don't include the port.
It should work on whatever port for that domain. I use :3000, :443, :8080 all the time.
False alarm, it was a firewall issue on the client's side. Thanks for the reply, and I'm sorry I wasted your time.