Here are a few tips that might help resolve your issue:

1. Check if the external hard drive is properly connected to the computer.


2. Make sure to wait until the hard drive fully loads.


3. Modify the folder preferences for OneDrive on the hard drive.


4. Check if there are adequate permissions for the hard drive folder.


5. Log out of and log back in to OneDrive.


6. Restart the external hard drive.