I would start with confirming your AP is working without the remote.
If you hit the red button it should engage heading hold, hit button again and it will release.
You mentioned you see the autopilot banner across the top of the screen- on my unit the banner is on the side when AP is not in use, and switch to the top when engaged.
If you confirm everything is working without the remote, I would then check the device list on the NMEA 2000 network. YouTube has many videos that walk you through how to get to this screen. Off the top of my head, go to main pages screen where you select your chart or sonar, ect. Top button settings, I can’t remember if there is another sub menu before device list. If the device is shown you could try removing device. I would also unplug it from your NMEA network and try to re install. I don’t have the remote personally but that is what I would do for a diagnosis. A phone call to Tim at Harbour Chandler or to Lowrance Canada may lead you some results. Both Tim and lowrance reps will be able to walk you through over the phone.