I got the error below, no clues about the nature of the problem.
Thanks for any help.

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[JavaScript Error: "uncaught exception: undefined"]

[JavaScript Error: "Error 500 for search 6NDUIRH2 in My Library:

ZoteroObjectUploadError: An error occurred"]

[JavaScript Error: "An error occurred" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1365}]

[JavaScript Error: "Made no progress during upload -- stopping" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1424}]

[additional errors removed — D.S.]