Diagnosis
The soundbar is stuck in Bluetooth pairing mode. This overrides the HDMI ARC input. It happens if the BT pairing button was pressed accidentally or a previous pairing attempt failed.
How to Fix It
Clear the Bluetooth mode. On the soundbar remote, press the 'Source' button. Cycle through inputs until 'HDMI' or 'D.IN' shows on the display. If you don't have the remote, press the 'Source' button on the soundbar itself. Wait for the display to change.
If That Didn't Work
Perform a power reset. Unplug the soundbar and the TV from wall power for 60 seconds. Plug the TV back in first, then the soundbar. Turn everything on and check the soundbar's input again.
Heads Up
Ensure the HDMI cable is connected from the soundbar's HDMI OUT (TV ARC) port to your TV's HDMI ARC port. A regular HDMI port won't work for ARC control.