From the Obscene Studio Manual
You need to start OBS with a special parameter so Obscene Studio Overlay has access to the Video Cameras:
On Apple Mac computers
Please make sure OBS is closed, then open a Terminal (Utilities > Terminal) and type the following code:
/Applications/OBS.app/Contents/MacOS/obs --enable-media-stream--use-fake-ui-for-media-stream
On Windows computers
Please make sure OBS is closed, then open a Command Prompt and type the following code:
"C:/Program Files/OBS Studio/obs.exe" --use-fake-ui-for-media-stream --enable-media-stream
The application may be installed elsewhere. Just look for it in the usual Windows folder for installed applications.