Copilot in Word can't read chat attachments; Word for web file picker shows “no token obtained”

What seems to be working for me, albeit intermittently but still more than say 60% of the time, is I upload a file through Word Copilot, tell it to do something, it then thinks for a while and returns the "can't read/file empty/corrupted" error. 

I then hit "/", the file I just uploaded shows up, I select that, copy my previous prompt and HEY PRESTO! the file is not empty/corrupted. 

Fingers crossed this has been working quite well for me (one more step but it is really inconsequential to my workflow given how much time Copilot saves me). 

One thing: I have not touched my OneDrive in a while. I usually clean up the files regularly, but have not muddled with OneDrive other than uploading files through Word Copilot. I am not sure if this provides any useful diagnostic information, or if it is more coincidence than causative, but just thought I would mention it.

Of course on the odd occasion hitting "/" doesn't show any files and then I close everything, restart, sacrifice a small animal, burn incense, turn salt and hope for the best...