I have a similar problem with "Webcam settings" app from Mactaris. Everything is greyed out, it's like if it cannot access any cameras including the built-in camera.
I use this app a lot to control my camera for Skype calls. This is preventing me from updating my main computer to Catalina now. I have not seen an update for this app....
Apps that use the camera now request permission, I guess this app, which has not been updated for a long time, does not do it properly. I am not sure... I have sent an email to the developers of the app but I have not received a response.
There is another similar app called "Webcam settings control" in the App Store that apparently works but I have not tried it. I emailed the developer to know if it worked under Catalina and he confirmed that it does.