Sounds goes on/off

Recently, we are noticing that there is no sound (picture intact) coming from any channel on Uverse. This most often happens when the TV is turned off for a while, like overnight, then turned back on again. I used to be able to restart my receiver to get sound back, but that's not working this time. Neither is rebooting the whole system. The odd thing is that, when I turn on something else like Netflix, I get sound and then going back to Uverse the sound suddenly appears. Could this be a connectivity issue?