Diagnosis
The main board's firmware likely crashed. This is a known software hiccup with the S95QR.
How to Fix It
Unplug the soundbar from the wall outlet. Unplug the power cord from the back of the soundbar itself. Wait 60 seconds. Plug the cord back into the soundbar, then into the wall. This performs a hard reset.
If That Didn't Work
Check your HDMI eARC connection. Turn off your TV. Unplug the HDMI cable from both the TV and soundbar for 30 seconds. Reconnect it firmly. Power everything back on.
Heads Up
If this happens repeatedly, update the soundbar's firmware via the LG Sound Bar app. A corrupted firmware version can cause these dropouts.