Black screen on FaceTime with webcam on Mac Mini

I bought an eMeet C60e 4K webcam from BH Photo to use with a new MacMini M4 running Sequoia. It was advertised to work with macOS both on the B&H site and on the eMeet site. It was plug and play and worked for 3 days. Now, I only get a black screen when I try to use the camera with FaceTime, Photo Booth, or Quicktime along with a message that the app has not received any video from the connected camera. The camera is recognized in System Information, both under USB and Camera, but does not show up under Video on the FaceTime menu bar (only option is for automatic camera selection -it does show up under Output for audio). It is grayed out in Photo Booth. This is what I have tried so far without success:

1) Restarted multiple times

2) Restarted in Safe Mode in addition to removing all peripherals

3) Tried every port on the mini. The camera uses usb a, so I used an adapter and also plugged into a usb c hub with a usb a port;

4) Used some terminal commands to quit any apps that use the camera

5) Signed out of FaceTime and signed back in

6) Erased all content and settings and restored from a backup on the day the camera worked

6) Checked for software and firmware updates

7) Ran first aid and diagnostics

7) Called Apple -- they basically told me that because the camera shows up in System Information, the problem is not on their end

8) Emailed and chatted with eMeet - they are located in China, so responses take 24 hours and no one on that end knows anything about a Mac - all their solutions were for Windows. Additionally, the last response said they were out of the office for 2 weeks because of a national holiday.

Because the webcam worked for a few days, I am hoping there might be something else I can do to fix it. Otherwise, I guess this will become a donation to my local library. I appreciate any help this community can offer. If this is hopeless, can you also suggest a webcam with mics that will work with my setup - I only use this to chat with family, so don't want to spend a lot (under $100). Thank you.