Authentication Error Cloudflare Tunnel

Hi, idk if theres a topic, bc I couldt find any

But heres my problem:
I just managed to get my Cloudlfare Tunnel domain to work, but now I dont get to login.
I just get this error
“Unable to fetch auth providers. http://ha.domain.eu/?auth_callback=1

Whats the solution?

Thx in advance
Simon