Problems with Web Panel after installation

Hi, I have installes Nextcloudpi the very first time and it worked out. I can access nextcloud via (safe connection). But if I want to switch to the Web Panel, the page cannot be found ( I can log on with local IP (192...*2:4443) but it says that website is not save (no certificate).

I tried to add my ddns address to the trusted domains in the Web Panel but that also fails with: “System config value trusted_domains => 20 set to string”.

Port 443 is set in the router.

Any tips.