I've suddenly found that files I've previously been able to share are no longer working. The error message was simply "Couldn't complete share" with no further details or anything helpful.
As a test I uploaded a new text file and tried to share that. This time I got a different message: "Can’t share file: We’ve interrupted your sharing activity because your files might contain phishing content."
I have no idea which file or files might be the issue, so I've deleted some old files that are no longer current (those are still in the "Deleted files") and left just the files I need to share.
What do I need to do to restore sharing?