Unable to share and sync files in XD 55.2 version

Here's the Adobe XD version and I'm working on Windows 10 (no updates pending)
I tried everything I could find on the forum (reinstalling XD and CC, restarting PC, updating everything, closing processes in the bcg, renaming the OOBE file, etc.)
The issue started when I couldn't sync and update one of my XD files. (screenshot #1)
(Updating and saving other files (shared with me, but not created by me) was really slow and turned up multiple errors along the way, and/or making conflict files.)
So I created a new one (which synced eventually), but then I couldn't send invitations to others through XD for some reason (screenshot #2). The error I got is "Storage full. Go on Published and delete links", but there's space in storage (2.4 GB of 1 TB used) and barely any links in Published (less then ten and I even deleted some just in case).
So I found a workaround and invited others through Creative Cloud, but now it won't sync the file again. The error says that it "cant upload a document". (screenshot #3)
So I tried saving the file locally and uploading it to the Sync folder, but that too is showing some kind of error. (screenshot #4)



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