iPhone Error - All Contacts lost!

I just installed NC (v15, updated to 17) on my new home server and wanted to sync my iPhone SE (iOS 12) with it.

I changed the address of the old NC server to the new domain and wanted to see if the contacts have already been synced just to find out that there is now 0 contacts in my NC and also 0 (from ~300) left on my iPhone.

I tried to change the settings to only display my phones contacts but it did not help.

  • Has this happened to someone else?
  • Do you think it is a bug in NC that it pushes an empty adressbook to the phone or an error of iOS?

This is a call for help if someone might have experienced something similar or could support me with some ideas how to recover the contacts (if they are still somewhere).

Thank you in advance.