I have a Roku Express purchased in June 2020. It worked fine for about 4 months but has lost its connection to the remote. New batteries. Unplugged/replugged, etc per Community advice. I have it connected to an old tv (not smart) but, when I select the HDMI2 (where it's plugged in) I get the Roku Home screen, so I believe the Roku "receiver" is talking to the tv. So, I purchased a replacement remote, but it won't connect either! I'm about ready to throw this stupid thing away and buy a competitor's product that offers live support. At wit's end!!
I don't know what remote you bought, but if there's no button in the battery compartment then it's a simple IR remote that doesn't require any pairing. The remote that came with it was definitely an IR remote. You can verify whether the remote is working by using a digital camera like the one in your phone. Point the remote at the camera and press a button on the remote and you should see a flash of light on the camera's screen.
IR remotes require a clear line of sight to the Express, so make sure there's nothing blocking the front of the Express.
You didn't fix this person's problem. I am having the same one. The remote (a simple one) DOES NOT WORK. It has new batteries and the Roku remote app on my phone does work. Do I have the wrong remote? There is a clear line of sight to device.
Remote uses IR, the cellphone app uses IP the internet, so having one work doesn't mean a thing for the condition of the other. Did you check to see if the original roku remote is transmitting IR by looking through a cellphone camera? If the remote shows flashes it alright and it probably means the fault lies in the roku itself, maybe it doesn't accept IR commands anymore?
I'm afraid it's the Roku itself since the remote does show a flash of light when pointed at my cellphone camera. BTW, it doesn't work with my cellphone either when I installed the remote function on it. So it looks like I will need to get a brand new streaming device. I won't get a Roku again, tho,' since this thing is barely 6 months old.
As said the cellphone app is controlling it via the internet, so it arriving via the wifi signal from your router, not directly from the cellphgone to your roku. You can get a wifi voice remote for about $20 at walmart, doesn't need IR to work on the roku.