So we just bought a brand new Wii, and bought an extra remote and nunchuck. When we synced the second remote it worked pefectly fine- we turned the Wii off for the night and played again the next day and again it worked perfectly but then today when we tried to play with the second remote the lights would not flash on it when we pressed a button and it's not synced anymore. Since it's brand new the batteries are completely fresh (we're using the ones that came with it) and we even tried new batteries but to no avail. We tried unsyncing both remotes, the first one synced back fine but it's just the second one with the problem! Someone please help!!
Try opening the battery pack, and click the red sync button, see if this works