v4l2loopback devices not showing in applications

I have been successfully using v4l2loopback, with v4l2sink in OBS, to "send" my obs preview panel output to Zoom. The v4l2loopback devices have recently stopped showing in Zoom, Firefox & Brave. However, I can confirm the loopback is viewable in VLC. I'm on: - Pop!_OS (20.10) - v4l2loopback-dkms (0.12.5-1) - OBS (with the v4l2sink plug-in) (26.0.2+dfsg1-1) - Zoom (5.4.3) I normally start the loopback device with the following: sudo modprobe v4l2loopback video_nr=99 card_label="OBS Video Source" exclusive_caps=1 This is usually run on boot via: $ cat /etc/modprobe.d/v4l2loopback.conf options v4l2loopback video_nr=99 card_label="OBS Video Source" exclusive_caps=1 $ cat /etc/modules-load.d/v4l2loopback.conf v4l2loopback The device shows via v4l2-ctl: v4l2-ctl --list-devices OBS Video Source (platform:v4l2loopback-000): /dev/video99 Cam Link 4K: Cam Link 4K (usb-0000:06:00.1-4): /dev/video2 /dev/video3 UVC Camera (046d:0990) (usb-0000:06:00.3-1): /dev/video0 /dev/video1 and once I start the v4l2sink in OBS, I can view this in VLC. However, as mentioned, the OBS Video Source device is no longer showing up in any applications that I've tried, as a selectable source. How can I get the OBS Video Source show up as a source in Zoom again?