NextcloudPi Docker start problem after server reboot


I set up yesterday a new nextcloudpi-docker server on an old x64 laptop with fresh installed light ubuntu 18.04 and all available updates. Then I pulled the x86-docker ncpi, configured it. Ran good. Then shut it down and rebootet tomorrow morning. Started the docker ncpi and got the same error as had with my rpi 3b+:

The webpage under :443 stays blank.

The same happened with my rp3b+ before.

I hope for some help, because I like the docker-idea and won’t to spam my Linux-server with testing software, which I maybe can’t remove fully.