Hi @Ray Russell ,
If the application is working on localhost but not when published, it is likely that you have an incorrect localhost reference somewhere in the application itself or in the application registration or manifest. Please make sure that you have updated your redirect URIs in your app registration to map to the published domain.
It is also possible that the user trying to login does not have permissions on the app or does not have the proper credentials.
In addition, the app my need consent with tenant-wide permissions.
If all of these settings are correct, try enabling web server logging under Platform Features > Diagnostic Logs and checking the logs for information.
Typically this issue is related to an app registration or code reference that is not updated to the correct domain, or a permissions issue, but if you share a screenshot of your error I will be able to better diagnose the precise problem.
If the information helped you, please Accept the answer. This will help us as well as others in the community who may be researching similar questions.