Failed to access "manage" after installaing nextcloud

After installing nextcloud as a plugin on freenas 11.3 and configuring the "trusted domain" sucessfully I cannot access nextcloud (clickung on manage) via the web interface because I am always automatically forwarded to https. Https always appears in the URL. I can manually open the URL via http, but after entering the user data, it will be redirected to https and get an error.