Yes, as I say, it's a problem with an upstream service. It will affect everyone — and many tools other than Zotero — until it's fixed, which hopefully will be within a few hours.
You can check the status of CrossRef's (the DOI provider) services here. Zotero uses the Public API and Content Negotiation. https://status.crossref.org/
Make sure you're running Zotero 6.0.2, and if you're still having trouble provide a Debug ID for an attempt that fails, if you're able to.
But doi is true... I tried several dois for several times, it still doesn't work, including what I added it before successfully.
And yes, I used zetreo for the latest version 6.0.2.
You should also post some example DOIs here.
10.1007/s12369-018-0501-8
10.1109/ICRA.2017.7989777
10.1109/TBME.2004.827086
10.1109/NEBC.2010.5458188
I'll try again later.
I am also experiencing the same problem with retrieving valid doi.
Is the issue still not fixed? Is anybody else still having this problem?
Thanks
There's no need for further posts on this until it's fixed — there's nothing we can do about this.