Some plugins normally needs to be updated to work with new OBS versions. Never update unless you already checked compatibility of the plugins you're using.
From the change log:
View attachment 120606
Sorry, but I really don't understand what advantage there is in removing the ability to monitor audio without sending it to the output.
I've been using OBS for almost 7 years, every single day for my live streams, and now I can no longer mute my microphone while still monitoring it through my headphones.
With the current monitoring behavior, the microphone remains live for the audience even when I mute it. The only way to stop it is to disable monitoring as well.
The shortcuts currently available in OBS don't provide any workaround for this issue. And since OBS doesn't even offer a single shortcut to both mute the source and disable audio monitoring at the same time, I don't think Elgato will be able to implement such functionality in their Stream Deck plugin either.
So I simply can't understand why "Monitor Only (mute output)" was removed, or why there isn't at least a single shortcut that simultaneously disables both monitoring and output.
In any case, having to completely lose headphone monitoring just because I want to mute the microphone for the audience doesn't seem useful at all.
In practice, a feature that has existed for 7 years has been removed without providing any real alternative.
Unfortunately, my only option now is to downgrade OBS and stop updating it for as long as possible. If this behavior remains, I may eventually have to switch to another streaming application.
Honestly, that's the only explanation I can think of for removing such a useful feature.