[Plugin: Zotpress] ZotPress working, but from time to time

Hello,
I seem to have a problem with ZotPress. It does always display the bibliography in the admin’s screen but it doesn’t always do so on my page.

Sometimes everything appears in order and sometimes all I get is a message “Sorry, but Zotpress encountered an error after attempting to contact the Zotero server. “. This happens without me changing any settings or adding anything to the library. I use normal settings and just want to display the whole thing.

If, however, I add special options like displaying by tag I only get the error message I’ve mentioned above.

I’m really quite helpless here as the problem isn’t a constant one. Might it be that my server lacks something switched on? like OAuth or something?

Any help would be much appreciated.
Best regards,
Wojtek

https://www.ads-software.com/extend/plugins/zotpress/