Topic: Wii Play Motion cannot detect Wii MotionPlus accessory.

I've got two old Wii remotes with 2 Wii MotionPlus accessories that you can plug into them. Despite being correctly connected to the remotes, when I try playing any of the first few games you can access on Wii Play Motion, it says the accessory is not connected to the remote. I have absolutely no idea how I can resolve this without replacing the remotes with ones with Wii MotionPlus built in. Has anyone else had this issue?
Also: I'm playing on a Wii U which is backwards compatible with Wii U games, and the Wii MotionPlus works fine on other games, even though I can never seem to calibrate it when prompted to do so.