I have a ONN UHD connected to a TCL tv with a Vizio soundbar. I have the remote controlling the tv and soundbar via IR. I tried CEC but couldn't ever get it working to my satisfaction.
Everything was great until a couple of weeks ago. Now, I can't control either IR devices when turning things on. Can't power on the TV, can't adjust the soundbar volume. If I turn the TV on using its remote, then after 5 minutes or so, I can control everything again, including turning off the TV.
I've forgotten and re-paired the remote, forgotten and reconfigured the external devices and buttons, and it works until I turn things off, and then I'm stuck again. I'm kinda at a loss for what to try now.
Might sound too easy, but try replacing the batteries for new ones. My ONN remote drained the batteries kinda fast. Instead of my remote dying, the IR wouldn’t work and kept unpairing it to my TV. Replacing the batteries has worked for others also.