Every doi I try leads to Zotero saying that lookup failed, including ones which I had used previously for other bibliographies I made. How do I resolve this issue?
There was a period about the time dvillar7 posted when CrossRef appeared to have some issues, so good chance this just will start working again. If this doesn't work, we do want a couple of sample DOIs, ideally ones that you know have imported previously, together with a debug ID: https://www.zotero.org/support/debug_output
Upgrade Storage
2. Try quitting Zotero and reopening it.
3. Provide at least 2 DOIs that fail look-up.
I've been using the Magic Wand repeatedly today without any problems or slowdown to find journal articles and book chapters.
For the experts to help you probably should also state your computer operating system.
If this doesn't work, we do want a couple of sample DOIs, ideally ones that you know have imported previously, together with a debug ID: https://www.zotero.org/support/debug_output