Try the following and pair again.

1. Ensure that the operating system of your mobile phone is Android 6.0 and above, or iOS 9.0 and above.
2. Ensure you have the latest version of the App installed on your smartphone.
3. Turn the phone’s Bluetooth off and then on again.
4. Please fully recharge the smart watch.
5. Make sure the smart watch is close to the phone.
6. Reset the smart watch to factory settings and pair again following the manual instruction.
7. If your device is currently connected to another phone and you would like to pair it to a new phone, first you need to turn off the Bluetooth of your connected phone.
   
   If the other phone is an iPhone, you will also need to delete the Trek smart watch from its Bluetooth device list after turning off the connected phone's Bluetooth. Go to iPhone "Settings" > "Bluetooth" > "My Devices", find the connected device and tap the ⓘ icon next it and then tap 'Forget this Device'.After that, use the Ryze Connect app installed on your new phone to search and pair with the device.
8. Restart your mobile phone.