FX Chrono re-pairing

Go in your Bluetooth settings and check to make sure scan is active while you try to pair. On my iOS it will not show paired in the BLE setting menu even if paired and working. 

The phone/tablet must have BLE which is different from the older Classic Bluetooth (EDR). As Elis5173 said, some Adroid devices require GPS to be enabled for the BLE to work with certain apps.
 
2 suggestions. probably not likely.

Perhaps the phone it was originally paired with is close and the FX is still paired to that phone and wont pair to another or it is interfering. If that is the case, turn off that original phone wiht the broken screen.

There was a app update for the iphone several months ago. It made pairing much easier and consitant.



Good luck