Thanks for following back up, KeepImmigrants,
We absolutely understand that AirDrop was previously working. The fact that it now is not is why we are suggesting the troubleshooting options we are.
We encourage you to see if the issue occurs while in a new user, if you haven't had a chance to: Set up users, guests, and groups on Mac - Apple Support. This will let us know if the issue may be related to a setting or process specific to your Mac user account that might be causing the issue.
Likewise, we would suggest seeing if you can replicate the issue in safe mode on the Mac: How to use safe mode on your Mac - Apple Support. In addition to preventing some processes from starting up when the computer boots, safe mode also runs a scan of your startup disk and makes repairs where it can. This by itself can sometimes solve a variety of issues.
We can also suggest trying AirDrop on another network and/or with other devices to see if you can isolate the issue directly to your network, Mac, or iPhone.
If you still need help after that, please get in touch with Apple Support directly. You can do that here: Get Support.
Have a wonderful weekend.