Specifying Application ID URL

Question

Context

I'm building an Office 365 add-in - to be run in Outlook, both desktop and web -, and I'm at the stage where I want to try logging the user in and getting an access token. However, I'm running into trouble getting the login to work.

The Troubles

I have registered the application in Entra, and I have an App ID for it. I filled out my WebApplicationInfo element in the manifest, and that's where the problems start.

Rejected sideloading

If I use the app URL Entra gives me, and get something like this