Not sure if this is the right place to post this, but I've been having lots of problems using cheese and I've been wondering if there is any good alternatives.
Thanks
Ok-
Is this a laptop or a desktop with a camera attached?
IF it's a webcam not built in to your pc than you may want to include what camera you have.
Well, since Pop OS is based on Ubuntu and Debian so there should be other alternatives for software for your webcam.
To find out why Cheese won't open try opening the terminal and just type chess and hit Enter.
If something is not right the terminal will return a message if it won't launch on it's own.
Than google the message.
Another thought is maybe the webcam needs drivers?
I'm not running Pop OS however; OBS Studio works great on my Sony laptop. Before I installed OBS I installed Kamoso and it worked out of the box.
Maybe give Kamoso a spin and see if it works for you.