Can't transfer files to external HD

[overflowingtruth]

I'm running Catalina (10.15.7) on my Macbook Pro. All of a sudden I'm able to transfer any files of any size to any of my external hard drives (connected via USB). When I drag a file over to the drive, my mouse arrow gets a white "no-smoking" icon indicating that I can't add the file there.

I need to unload files from here so I can create some more room. Please help!

 

[Lufbrarunner]

Have you checked the 'Permissions' for the files and the target drive?

 

[overflowingtruth]

Thanks for the suggestion. I have Read and Write permissions for the drives and the files. It is literally happening with any file and any USB drive I try to put in. Very strange.