Messages app will not send attachments, images or video

There are several threads on this topic but most of them are years old. Looking for a fresh and reliable solution that will enable me to send attachments in Messages on the Mac. (Catalina)

I've always been able to send pics and videos via the Messages app on Mac OS. And now suddenly, nothing will send. The blue progress bar gets to about 90% and then just hangs there until it times out.

The only work around I've found is to Airdrop the image to my phone and text it from there- annoying.

Oddly enough if I copy a gif or pic from Google images and paste into Message, those send just fine. But if I drag or share an image from the Finder (no matter how small a file) it won't send.

My software is updated. I've signed in and out of Messages and have rebooted several times. I'm connected to the internet via an Ethernet cable.