You just need to resynchronize them

There is a synchronize button inside of the battery cover, you have to press it at the same time while pressing the one on the wii.

you don’t have to hold the button, just press it. and don’t forget to press the synchronize button on the remote too

Hold the square red sync button on the wii for a few seconds then tap the sync button on the remote quickly once or twice. Wait…………after 20 seconds if it doesnt work try again, maybe hold the sync on the wii and press the wii remote sync button then let go of both of them. Its kinda weird sometimes it works sometimes it doesnt. Let me know if i helped! ^_^

Thanks!