TCL 5-Series Roku TV S555 ARC or eARC soundbar audio is not working

The checks in more detail

Then check the TV's audio output setting. In Settings, Audio, Audio output or Speakers, choose HDMI ARC rather than TV speakers, and make sure the TV is not set to Automatic with a fault. Set the digital audio format, called Audio mode or HDMI audio format, to Auto or to PCM: PCM is the safest, because most soundbars decode it, while a surround format that your soundbar cannot decode leads to silence. Check the soundbar's own input is set to the ARC or TV input, and its volume is up. Remember that some sources, such as Dolby Atmos, need eARC, and the S555's support may be limited to standard ARC, which carries compressed surround.

If the sound drops out or buzzes, replace the cable, since a poor HDMI cable breaks the ARC link. Power cycle everything: turn off the TV and the soundbar, unplug both for a minute, and start the soundbar first. Update both devices' software. If lip sync is wrong, use the audio delay setting on the TV or the soundbar. A volume that cannot be changed by the TV remote means CEC is not working; use the soundbar's remote or a learning remote. Try the optical output, if both have it, as a test of whether the soundbar is at fault. If ARC never works with a good cable and the right port, contact TCL with the model number.

If the soundbar worked once and then stopped, the usual trigger is a power cut, a software update or a changed input, which reset the ARC link; turning CEC off and on at the TV and the soundbar, then restarting both, often restores it. Some soundbars take a minute after power-on before they accept the TV's audio, so wait before judging. A soundbar plugged into the TV's ARC port and also receiving a game console directly can switch inputs unexpectedly, so keep each device on the input you want. For Dolby formats, check that the soundbar shows the format it is receiving on its display, which tells you whether the TV is sending what you expect.