did you use your webcam twice in OBS ? delete all webcams sources in your scenes !
most wecams didnt support multi output so i can come to problems
check the windows Kamera Privancy Settings if OBS has Permission to use the Webcam!
my solution for use the webcam in OBS multiple times is
Create a Scene name it "WEBCAM FULL" Add the Webcam as source to it
View attachment 67628
when you need Filters Create a Scene name it eg "Webcam - Greenscreen Filter" and add the "Webcam - Full Screne" scene as source
View attachment 67629
now add the Filter to the "WEBCAM - Greenscreen Filter" Scene
View attachment 67630
you see the Webcam has the only the filter on the greenscreen scene ans this can be used as source in other scenes as webcam i used it on this way to usw the virtual webcam with the webcamfilter for obs ninja and discord ! at the same time i used it in OBS