I have a brand new U2713 hooked up to DP on a new Macbook Pro. I hooked my external speakers (not a Dell soundbar) to the audio out of the monitor. I was on a GoToMeeting and sound was fine and then it cut out. GTM showed LED gauge of audio activity even though I couldn't hear it. I then flipped GTM audio to the laptop and it turned on. I flipped it back to the U2713 and it turned off. Ended up finishing my GTM with audio out on the mac.
Went to sound controls and when I double click an alert sound, if U2713 is selected, it does play. If I change to Internal speaker it does.
I unplugged the U2713 for a few seconds, plugged it back in and the sound control test still failed. Very odd, the sound was working yesterday through the monitor.
Any ideas?