Videos not playing

[Ert_12]

When I have multi output device selected youtube and vimeo don't play however when I select headphones setting they play but then the sound does not record.

 

[MarioSBJ]

I have the same issue. I formated the computer to check if this would solve... no success. When I select Multi-Output Device, the videos get stuck, as if I don't have an internet connection. Sometimes the videos playback, but the audio is distorted.
iMac with Catalina Mac OS 10.15.7
OBS 26.1.2
iShowU installed