Empty content by browser access

Finally I got the impression that my backup (I followed How to backup and restore using nc snapshot ) was somehow defective so I gave up debugging of errors.

Instead I restarted from scratch with the provided image (v1.48.3 thank you very much!). Somehow I managed to restore the data from my automatic nc-snapshot-auto inspired by the explanations “How to backup and restore using nc snapshot”.

…and run into a lot of new challenges (manual copy of all data to the new instance, adjust permission, re-scan, Cannot login: Too Many Requests, …), which seems to be overcome finally except one:

Although I can access the panel within my local network this situation is not very satisfying…

Any idea?
No complains in www .domain.net/settings/admin/overview
Nothing special under www .domain.net/settings/admin/logging

Thanks a lot.