I struggled a bit and had not been successful in pairing the Plantronics C720-M headset bluetooth with my Android mobile phone.
The phone (or any other mobile phones) for some reasons just couldn’t detect the headset!
But thankfully I’ve realized the solution:
1. Open this document and use it as your guidance. Enable Bluetooth on the Mobile phone.
2. Disable/turn off Bluetooth on the headset by pressing the “Mobile Talk” button for few seconds until you hear “Bluetooth is off”.
3. Press the “Mobile Talk” button again, not just to turn on Bluetooth, but also to pair it. Keep pressing the button until you hear “Pairing”.
4. Voila, the mobile phone then is able to detect the headset and after few seconds pairing is successful.
My mistake was that I stopped pressing the button when Bluetooth is turned on, while the instruction asked to continue pressing after it until you hear the word “Pairing”. Thanks!