TCL 4-Series Roku TV S455 will not pair with Bluetooth headphones or speakers

The checks in more detail

Check what your S455 offers: open Settings, Remote and devices or Settings, Audio, and look for Bluetooth or Wireless speakers. If no such entry exists, the TV does not support direct Bluetooth audio, and the answer is a different method rather than a repair. If you do find a Bluetooth menu, put the headphones in pairing mode close to the TV, remove any old pairing from the TV and pair again, and make sure the headphones are not connected to a phone, since most headphones connect to the last device and refuse a second.

Update the TV in Settings, System, System update, because Roku adds features this way. If the audio is out of step with the picture, the TV's audio delay setting in the sound options, or a headset with a low-delay mode, can help; wireless headsets add delay of a fraction of a second. A Bluetooth transmitter plugged into the TV's headphone or optical output is the dependable alternative: choose one that supports a low-delay codec and pair your headphones to it. The Roku app's Private Listening is the easiest route:

install the Roku app, connect the phone to the same Wi-Fi as the TV, open the remote, tap the headphone icon and plug in or connect headphones to the phone. It works with wired headphones and with Bluetooth ones connected to the phone, at the cost of a little delay. Keep the TV and phone on the same network, and use the 5 GHz band if the TV is in range. If the TV's own Bluetooth setting exists but pairing fails, restart the TV by unplugging it for a minute, do a factory reset only as a last resort and contact TCL with the model number from the back.