This is still an issue 10/2022.

I have tried all the solutions mentioned and nothing works. There are no special characters in the file name. 

What's Frustrating is that I was uploading the exact same types of documents just a month ago with no issues, and now for some reason any receipt I try to attach to an expense gives me this error message. 

It would be extremely helpful if QBO could at least include an "information" icon explaining what type of document is flagged for security reasons.

Very frustrating.