This has been fixed! If you are still getting this error please open a support case from your Azure Portal
A change in the backend could result in seeing this error in your verbose application logs. A fix is scheduled and when uploaded this blog will be updated. This only affects a subset of customers and not all customers.
Users logging into the application for the first time receive the following message “You do not have permission to view this directory or page' after signing in and the url in browser is ‘https://<appname>.azurewebsites.net/.auth/login/aad/callback' and cannot log in.
1. Click on “Manage Application” and then “Manifest”
2. In the "requiredResourceAccess" section, look under the following resourceAppId 00000003-0000-0000-c000-000000000000. If you see the highlighted section with the id GUID 311a71cc-e848-46a1-bdf8-97ff7156d8e6, remove the highlighted section and save the change to that manifest file
Let us know if this helps. We will update this blog when a fix is pushed out.