Paramount plus content not streaming in the Apple TV plus app on Mac

I activated the free trial Paramount plus channel subscription in the tv plus app on my MacBook to watch Star Trek SNW. Two things I noticed:

• the first two episodes are for some reason not part of Paramount plus, so I had to buy them (no biggie)
• the other episodes do not stream through the Paramount plus channel. Sometimes they start for a few seconds (showing the Paramount logo building up), sometimes they continue with a black screen and no sound (though a single time with subtitles), but usually the streaming window closes again after a fraction of a second.

I do not get any error message. I don't think it is a DRM issue, since they do seem to start for a few seconds. I can stream all the Apple TV content without issue. I could download the episodes through the Paramount plus channel without issue, but the episodes would still not start. I tried a few other shows in the Paramount plus channel, but with the same results.

The system is up to date.

If it matters, I have an Apple account registered in Germany, but I am currently in Serbia. But again, the shows sometimes start for a few seconds, before aborting, so I don't think it is an issue of streaming rights. Also VPN.

Any more leads I could follow?