When trying to access a Azure Application Proxied app the Microsoft login prompted is repeatedly presented to the user and they cannot access the website.

To fix:

1. Go to Azure Active Directory
2. Select “App registrations”
3. Select the affected app
4. Select “Authentication”
5. Under “Implicit grant and hybrid flows” tick the boxes:
6. Save the app
7. Try to login to the site again

The app should then allow you to access the website after entering your Microsoft credentials.