Solved! Have a 55S517 TCL SMART TV and a VIZIO S5451w-C2 sound bar. Followed all hook-up instructions for the (ARC) and even a couple

They *should* work. I assume you verified both pieces support ARC and enabled?

Always try another cable, and never mind "this cable worked before" or "this cable worked somewhere else." and keep that cable under 6' or am out.