Hi Brian,
Thank you for sharing your question. I understand that you are having issues seeing that OneDrive has too many files’ errors for a folder you deleted ages ago. I am here to help.
Based on my knowledge this can happen if OneDrive hasn't caught up with the fact that you deleted the folder. It might still be trying to sync it or has it stuck in its system somewhere.
Here's a fix you can try.
First, restart OneDrive – this makes it rebuild its system and forget about the old folder. Press Windows + R to open the Run little box.
Write this in the box.
%localappdata%\Microsoft\OneDrive\onedrive.exe /reset
Then press Enter.
If you see a message that says Windows can't find... try one of these instead:
C:\Program Files\Microsoft OneDrive\onedrive.exe /reset
Or C:\Program Files (x86)\Microsoft OneDrive\onedrive.exe /reset
Once it restarts, OneDrive will begin syncing again. If it doesn't restart by itself, just open it from the Start menu.
Also, take a look at your OneDrive Trash online. Sometimes deleted folders hang out there, messing things up. Go to OneDrive's website, hit Recycle Bin, and empty it if you need to.
May I also ask did you remove the folder from your computer or straight from OneDrive online? Also, is this OneDrive for your own stuff, or is it through work or school?
I hope this answer is helpful, if you have any questions, feel free to reply.
Best Regards,
Noel