Apologies for the delayed response from over the weekend.
Based on the issue description, it looks like you are working on registering an application in the Azure portal, as outlined in this doc : Register an application with the Microsoft identity platform
As for as the URL that you had shared/admin center portal, it works fine for me. Just to isolate, if you haven't done this already, you may try clearing your browser cache and cookies: Sometimes, cached data can cause issues with website access.
Since you have posted the question on Azure App Service tag, just to clarify are you leveraging Azure App Service for hosting WebApp/domain?
Kindly let us know with more details, we will follow-up further.
-We may have to re-tag to receive insights from the targetted SMEs/audience.