XR15 remote won’t change television channels

You mean won’t change channels on the cable boxes, reset the cable box

Because I have an Xfinity Flex and it came with the XR15 remote.
I don’t want to use a bunch of different remotes.
I want to use the remote that supposed to work.

Then why are you using a cable remote to work your tv? That’s not how it works. Use your actual tv remote. Comcast remotes are not a universal remote

“You mean won’t change channels on the cable boxes, reset the cable box“

No, I mean it won’t change the channels on the television.
I don’t have a cable box because I don’t have cable television.

Xfinity Flex is a cable box.
Xfinity remotes don’t change the channels on your tv but the cable box and that’s all their meant to do. If your brand of tv needs an ok push to change inputs (not channels), the Xfinity remote won’t provide it, you’ll need to use the tv remote