Current OBS does not natively support Mac OS 10.15 (Catalina), however, there is a workaround before it’s supported:
- Open Terminal application (you can find it in the Spotlight Search)
- In the window that opens, paste in the following code, then press Enter:
open /Applications/OBS.app/Contents/MacOS/OBS --args -picture
- Accept all security alerts to allow Terminal to access the cameras and write files to Finder. They will pop up as you use OBS.
- Keep Terminal open while you run OBS