Cloudflare Proxy / Cloudflare Tunnel

Hi,

When I connect to nextcloud via Cloudflare Proxy or Cloudflare Tunnel, I can log in and see the dashboard, but I can’t click on the icons.

(Cloudflare Proxy or Cloudflare Tunnel) -> nginy (Reverse Proxy)->Apache (nextcloud)
                Public domain                port:443  Local domain  port:4444 HTTPS

When I call nextcloud from the local domain, everything works. What also works is when I turn off cloudflare proxy my IP is visible or with cloudflare tunnel I have to open ports on router / firewall.

Other services like wordpress work via cloudflare proxy or cloudflare tunnel.

Does no one have any idea what the problem could be?