After you replace the battery in your Oculus Go or Pico G2/Pico 4KS/Pico Neo 3 controller, you may need to sync it to the headset again before it starts working.

Pico G2/4KS: Press the Home button. The indicator light will begin blinking. When the light turns off, the controller is synced.

Oculus Go: Make sure the headset is nearby and then press and hold both the back button and the Oculus button at the same time until a light starts to blink on the controller. When the blinking stops it is reconnected and you may resume training.