Diagnosis
The wireless link between the soundbar and the subwoofer has been lost. A solid light on the sub means it has power, but it's not getting a signal from the soundbar.
How to Fix It
You need to force them to re-pair. Here's how: 1) Unplug both the soundbar and the subwoofer from power. 2) Wait a full 60 seconds. 3) Plug ONLY the subwoofer back in. Wait for its light to go solid. 4) Now, plug the soundbar back in. It should automatically start searching for the sub. You'll usually see a pairing light blink on the soundbar, and after 10-30 seconds, you should hear a deep bass tone from the subwoofer confirming the connection.
If That Didn't Work
Move the subwoofer. Sometimes physical obstructions or interference from other wireless devices (like a new router placed nearby) can block the signal. Try moving the subwoofer right next to the soundbar, re-pair, and see if it connects. If it does, you've got an interference issue. Find a new, closer spot for the sub.
Heads Up
The pairing process is automatic when you power up in sequence, but it can be finicky. If the subwoofer light is blinking, it's in pairing mode. If it's solid and not connecting, the re-pair sequence above is your best bet.