So for verification you can run the git clone command successfully however the git repository plugin is not working correctly. Correct?
I have experienced this behavior before and typically it occurs when the Repository URL is incorrect. I have noticed that the git plugin is rather sensitive with the Repository URL.
To verify what is the secret value? Are you using password or Access Token.
With that being said I can test this in my environment and get back to you.
Regards,
Andrew
Regards,
Andrew