OBS LOG ???
OBS Studio creates a log file each time you run it which contains very useful diagnostic information. Without a log file, it's much harder for any support volunteers to figure out problems and your post may be ignored. To upload a log file, go to the Help menu > Log Files > Upload Last Log...
obsproject.com
did it work in other programms like VLC
have you setup the card in obs to the right resolution
Capturecard type?
Connected to USB3?
more devices on the same USB root hub ?
try this programm to find it out