Diagnosis
The infrared (IR) sensor on the soundbar might be blocked, or less commonly, the remote itself has failed.
How to Fix It
First, clear the line of sight. Make sure nothing—like a game console, decorative item, or even the TV's own base—is sitting directly in front of the soundbar's right side where the tiny IR sensor window is. Dust it off with a dry cloth. Then, test the remote up close. Point it directly at the sensor from about a foot away and press a button. If it works up close, something was blocking the signal.
If That Didn't Work
Test if it's the remote. Use your smartphone's camera (the selfie camera usually works). Point the remote's IR emitter (the little bulb at the front) at your phone camera and press a button. You should see a faint purple light flashing on your phone screen. No light means the remote is dead.
Heads Up
Universal remotes or TV remote control setups (like HDMI-CEC) can sometimes interfere. Try turning off CEC control on your TV temporarily to see if the Polk remote starts working again.