CSV Import of "Issues" don't work

Problem to solve

I try to move over from Gitlab.com to a self-hosted version.
I’ve exported the issues as CSV from gitlab.com > Tab: ALL.
I’ve imported this file into my self-hosted gitlab.

I got a message, that I will get a notification by Email, if done, but there isn’t any notification after 1 Day.
How can I check if the process is still pending and if there are any errors which prevent the import.

BTW: It worked some time ago, as I initially setup the new server. I’ve imported round about 635 Issues with this method.
Now I want to import the issues that are added in the meantime to gitlab.com, as we like to fully switch over now, but the above described error occurs.

Versions

Versions
Online-Version 17.0.0-pre
Self-Hostet Version 16.9.1

Question:

Where can I find some logs about the import process. Maybe there I got some detail information why there isn’t imported anything.