Redirect Nginx Proxy Manager to own Subdomain

[ZZELAV]

Hello together,
I am running my Nginx Proxy Manager on sub.example.com:81 and want to redirect it to proxy.example.com. I have set it up in the Proxy Hosts and in my DNS Entry and everything is working up to the login.

When I access proxy.example.com I can login, but that I get redirected back to the login page of the Proxy Manager. Is there a possiblity to fix this?