I had a Streaming Stick + and everything was fine. I purchased a Onn Roku soundbar a d the remote will not work with the TV power. The old one did. I can’t set up the new remote in settings as it says it can’t find a remote even though it came with the soundbar. I can adjust the volume of the soundbar just not TV power. There is no pairing button on the remote. Doesn’t make sense. Why the old one worked and this one doesn’t. No, I do not have ARC or CEC etc on my TV. HDMI 1 works just fine.
Your new remote is IR only, no need for pairing. And the reason you can't program a tv brand in is the tv controls on the onn soundbar remote are roku commands that NEVER change. When the roku sees these tv commands it initiates a cec commands over the hdmi cable to control whatever tv brand is connected. All tv brands respond to same cec commands no matter what brand they are. So for it to control the tv power of the tv you will need cec on your tv and it will have to be turned on. Then go into the tv settings and refresh the cec devices connected to it.