Follow the steps in the Reporting Startup Errors section of the Reporting Bugs page and let us know what appears in the Error Console.

Dan--
restarting my computer got me back Zotero back on my desktop--wow, how obvious. I filed error Report ID 1323618794 from my desktop. The Error console showed [non-Zotero message removed — D.S.]. There was no pink background (as Reporting Bugs instructions described), but clicking on the error title gave me a whole page of stuff, which I can post to forum if you want. Neither the server nor my desktop library shows the material I added 4/27, but the sync arrow is acting normally. (I haven't tried to add anything since 4/27.)

As for my laptop: it continues to show the new material from 4/27. Hovering over sync arrow gives me :"last sync: Not yet synced". "Report Errors" was grayed out. There were 2 zotero errors listed in the error console: [unrelated messages removed — D.S.]

Any further advice? (I saved the new notes I added to Zotero items on my laptop 4/27 separately, so I could re-add those library items and paste in my notes manually if need be; but I would like the 2 computers to sync.)

One more piece of info that may/may not be relevant: I have many attachments to library items (not the new ones) which I have in the past been syncing via a little program a friend set up on my 2 computers, rather than using webdav. The last time I used the program was about 2 weeks ago. All problems have cropped up since 4/27. I suspect this is unrelated.
Thanks.

Hi Dan--1.5 hours later, still syncing--"getting updated data from server"

still.

Hi Dan--I took your advice and went through the entire rigamarole (same screens to reconcile etc.) But with the new version, the computers have synced! YAY. Thanks for all the hard work you do keeping this working.
Marian