Update: getting data works fine. INSERT had two issue.
1.) One table cell was left blank. Even though it was so on the old (EE) VPS. So I gave it a "" value.
2.) Date input failed for strange reasons, rtrim failed:
$ebaytime = $resp->timestamp;
$ebaydate = rtrim($ebaytime, 'T'); // did not work
$ebaydate = substr($ebaytime, 0, 10); // works
Example of eBay time: 2020-07-13T08:36:32.393Z
I am using php 7.4 - rtrim should work. Anyway, everything works now.
It helped to get an error output: