Diagnosis
The capacitive touch panel on the top of the soundbar has failed or become unresponsive. This is a known fault with the control board.
How to Fix It
First, unplug the soundbar from power for 2 full minutes. Plug it back in. This resets the main board and can temporarily restore touch function. If it works, the issue is likely a software glitch. Update the firmware via the Polk Connect app if available.
If That Didn't Work
The touch panel ribbon cable may have come loose. This requires disassembly. You must remove the top grille and check the connection between the touch panel and the main board. Reseat the cable connector.
Heads Up
If the touch panel is physically dead, the entire main control board assembly needs replacement. You can still use the remote for all functions. Do not attempt to clean the touch panel with liquid while the unit is plugged in.