I took the tag. Why do the tag vs download differ? However, I downloaded the tar.gz and replaced it with the current installed version. I’ll report back if this changed something.
Regards,
To all the readers here:
The issue has been solved.
The people from the posts above have been in direct communication and identified the problem. The DNB plugin will be updated shortly.
First, it now supports data delivery via WebDAV. Second, there was a problem when using a proxy server. With one of the latest updates, OJS changed settings from „http_host“ or „http_port“ to „http_proxy“ and „https_proxy“. This had not been taken into account by the DNB plugin. It will be fixed with the next release of the DNB plugin.
Thanks to all those involved for the great detective work!