What's the difference between Blue Tooth and Blue Tooth LE?
Standard Bluetooth: devices can be paired through system settings and has profiles to provide communication like a serial port.
Bluetooth Low Energy: This must be connected through code (unless encryption is on), and after connection, a code must be employed to read/write to the device with short data packets. If you were able to pair through system settings, you could not communicate to it without code written using system frameworks.
Bluetooth LE devices don't pair through system settings on IOS. Generally, you don't pair with Bluetooth Low Energy devices at all. The only time that pairing is required is when the device has an attribute that is marked as encryption required - attempting to read this attribute will trigger a pairing process, but before you can read you need to discover and connect to the device. Discovery and connection is handled by the Core-Bluetooth framework. The Core Bluetooth Programming Guide goes through the steps required to use a CBCentralManager to discover and connect to a BLE peripheral.
IDTECH's BTPay Mini is a Bluetooth Low Energy product which means pairing of the device happens through the IDTech SDK using Core-Bluetooth framework, not through System Settings -> Bluetooth..