Hello, my problem is, that the last attachments (PDF files) are not synchronized respectively uploaded. According to your documentation (https://www.zotero.org/support/kb/files_not_syncing), I tried Sync → Reset pane of the Zotero settings on Computer A and select Reset File Sync History for my library. As this did not work, I submitted the debug file (D826631647) and this discussion. Thanks for your help.