Hello rxwiz775,
Thank you for using the Apple Support Communities. I understand that you're having some AirDrop issues since updating to macOS Catalina.
Which exact iMac model are you using? Identify your iMac model
It sounds like you've done some good troubleshooting already, and the details help to rule out a few possible causes. To clarify, are you able to use AirDrop between your iPad and the Mac? Knowing this would help to further narrow things down.
Does it help if you restart both devices and test again?
It might help to boot your Mac into safe mode and then test again: Use safe mode to isolate issues with your Mac. This would help to rule out certain software causes. Testing in a newly-created administrator account is a great idea as well, which tells you if you have a system-wide or user-specific issue: How to test an issue in another user account on your Mac
Once you've tested both safe mode and a test user account, feel free to reply back with the results.
Have a good one.