Entra ID (Microsoft) not working

[PaulTorm]

Hi you all,
I just recently started a Project for my University where I wanted to use multipass. We are required to use Entra ID as our Auth Server.
I have run into a problem, that I just cant wrap my head around. At the Point where the auth server returns the code to my flask app, an JSONDecodeError appears.
Have i misconfigured the Microsoft End of my Application or are there any other possible causes?
FYI: I have already tested a OIDC connection to a keycloak - this works absolutely fine.
Im happy for any help and can also provide more infos if needed.
Cheers, Paul