I have a docker container with OICS 3.0.0 (same problem with 2.0.0). The container is behind a caddy self signed certificate.
When I try to login with correct credential I see this error.
this is my configuration env file
It seems the hostname ocis.osaspace.it resolves to 127.0.0.1 inside the container. So there seems to be an issue with the /etc/hosts or DNS. It needs to resolve to the IP address of your reverse proxy. So that ocis can reach the .well-known/openid-configuration endpoint via the OCIS_URL.