Question / Help Mac OS Catalina problems-cannot turn on camera and audio

Hi, I just upgrade my MacBook Air to Mac OS Catalina last night. After that when I turned on OBS and I found that I cannot use my facetime camera on my MacBook Air, even I cannot use audio input. The worse was that when I chose a facetime camera in the setting and the OBS was shut down. I erased the OBS in my Application Support and reinstalled it several times but the problems were still there. Does anyone have this kind of problem and could show me how to solve it? Thanks.