Yes, it never worked, I have deployed the starter pack, created a fresh user from there and sign in still doesn't work. This leads me to beleive that it's something to do with configuring AD B2C in the portal. I deleted the applications ProxyIdentityFrameworkExperience and IdentityFrameworkExperience, and set them up again, and it still doesn't work.
Stuck on this for a week now, and don't know what to try anymore.
Fixed it. I deleted the apps, and ran this tool https://aka.ms/iefsetup
Then just re-uploaded my custom policies with new App Ids, and Sign In works now.
Thank you very much.
Thanks for the answer!
Unfortunately, it still behaves the same, I Triple checked the ProxyIdentityExperienceFrameworkAppId and IdentityExperienceFrameworkAppId in the Extensions xml, and they are good.
I checked the permission for user_impersonation
And it looks okay to me. Anything else in mind I can check that might be causing this?