Check to see if it is connected to your Hue Bridge by navigating to Settings > Accessories. If you cannot see your device, it may have been accidentally disconnected from the system. In this case, add the Hue Tap switch back to your system in the Hue app:
1. Go to the Settings tab.
2. Tap Accessories.
3. Tap the Add accessory button and follow the on-screen instructions.
If you still cannot connect your Hue Tap switch, contact Philips Hue Support.