I've encountered the 'unauthorized_client: The client does not exist or is not enabled for consumers' error while trying to use authentication via Microsoft Graph in my web service; any ideas on how to fix this?

Question

Hello, I've added authentication via Microsoft Graph to my web service. Everything was working fine, but at some point, I started getting an "unauthorized_client: The client does not exist or is not enabled for consumers" error when trying to authenticate. Even creating a new application led to the same result. Has anyone encountered a similar issue? Any help would be greatly appreciated. Thank you!