Make sure that watch/band is in Bluetooth pairing mode.
Restart watch/band and search for the watch/band again.
Make sure that watch/band and the other Bluetooth device are within the support Bluetooth connection range (10 m). The distance may vary depending on the environment the devices are used in.
When pairing with an iOS/Android phone, make sure that the device has been removed from the last device's list of paired devices. If it was paired before make sure it is also removed from PLAYFIT App, then go to Settings > Bluetooth, touch the Settings icon behind the Bluetooth name, and touch Forget This Device. Then, pair them to connect the devices again.