I helped a colleague recently with an issue where Jabber wasn’t playing audio. I had a hunch it was related to an issue that’s cropped up a few times.
So I checked system settings, which were fine. Checked system settings for the Jabber app, and those were fine. Stumped, I poked around in Jabber’s settings, where I discovered it had ignored both the system settings, and the system settings for it, to try to send audio to her speakerless computer monitor.