Have you set up the appropriate Audio Source in OBS Studio?
My first step - make sure Audio working with OBS Studio not running (not in background, NOT running). Use native OS tool to confirm Audio... then (and only then) add Audio Source into OBS Studio
It appears you added Video source (the capture card)... have you added Audio source? ie did you route audio into capture card (and is capture card configured correctly to pass that along)? Again - check at OS (not OBS Studio) layer first
Or you mentioned Focusrite to computer . . are drivers, sampling rate, etc all setup correctly?