Sorry to hear that! Are you able to hear the sounds? Does it show activity on the monitor? Are any of its audio channels unchecked in the audio properties window?
It operates similarly to an alert box (they're both browser sources) so if you have one of those that's working, if the settings are the same they should act the same! Sometimes, OBS can just be a bit fickle and needs to restart to get some audio stuff to start working properly even if all the settings are correct.
If you're unable to sort it out, feel free to message me on Twitter in case this ends up needing a longer conversation!