Hi @Anonymous ,
Have you already made sure that the reply URL you have set up under App Registrations in the Azure portal matches the reply URL you have set up in the code? It should be in the Apps.json and might be referenced in other places too.
If you're testing locally it should be the local reply URL but if you've published the app you can use the published app URL where you want the user to be redirected. Just make sure that the references match in both the portal and the code.
Also make sure that the Tenant ID and application ID are set correctly.