I'm having a similar issue. I open my Zotero app on my laptop and it says that I must restart to complete previous upgrade. I restart (and did this multiple times) and the same message comes up when I try to open Zotero. Suggestions? I don't want to lose the references in Zotero, otherwise I would remove the app and try to upload it again.
Thanks. I tried to uninstall and it says I must restart to complete previous upgrade first. I went into my settings to uninstall and that did not work. I will try through my tech support and see if they can help. I'll let you know of the solution.
You should try reinstalling Zotero from the download page. Your data won't be affected.
I didn't say to uninstall — I said to reinstall. Did you try that?
You should also go to C:\Users\[User]\AppData\Local and delete the "Zotero" folder if one exists.