Bluetooth never Connects to Phone

## Prerequisites
- [ ] I have searched open and closed issues for duplicates.

## Describe the bug
Bluetooth never connects on my **external Bluetooth adapter** (USB) to my Phone
Clicking on 'Pair' button, the status below the device name in the switchboard plug shows 'Pairing' for a few seconds, then shows 'Unable to Connect' for a fraction of a second, and shows 'Available' again. The device is not paired to the PC. The indicator also shows 'Not Connected'.

On the phone (running **Android 9**), if I click pair, it shows 'Connecting' for a few seconds and then shows 'Unable to Communicate with PC'

### To Reproduce
Steps to reproduce the behaviour:
1. Go to Bluetooth plug in switchboard
2. Click on 'Pair' on any available Bluetooth device.
3. Watch as the status shows 'Pairing', the flashes 'Unable to Connect' and then, reverts back to 'Available'
4. See that the device is not paired no matter how many times this is repeated.

### Expected behaviour
The device gets paired and data transfer over Bluetooth is possible.

### Screenshots or screen recordings

## Platform Information

- OS: elementary OS
- OS Version: 5.1.4 Hera
- Hardware info
lsusb output for my external bluetooth adapter:

Bus 002 Device 003: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)

- [ ] I'm using the latest version from git that I've manually compiled
- [x] I'm using the latest released stable version

## Additional context
I've tried this on a couple of phones and Bluetooth connects to none of them.