The credentials dropdown of a Multibranch Pipeline with GitHub branch source shows "Exception Validating Credentials" when using a GitHub Enterprise Server:

The scenario when this happens:

• the credentials selected are to be used for GitHub Enterprise Server and not `github.com`
• the recommended "Repository HTTPS URL" is selected and properly filled

I believe that the check is still looking at the information in the "Repository Scan - Deprecated Visualization". If you select "Repository Scan - Deprecated Visualization" and select the correct "API Endpoint", then the credentials check will work.

The form validation is a red herring and the true way to validate the credentials against the "Repository HTTPS URL" is to use the *Validate* button. If that works, then the credentials should work for scanning and checkout.