Thank you for your reply, Andreas.
During the pairing session, my phone shows two names for the Bluetooth LE module, Makeblock AND Makeblock_LE. I mistakenly chose the latter for the pairing. Now, I was able to connect the Bluetooth to my phone using Makeblock, not Makeblock_LE. That solves the problem. Note: the phone doesn’t ask for a password during the pairing session.
BTW, are you able to utilize Makeblock_LE instead? Pairing is not required with Makeblock_LE. Only you need to move your phone closer to the device in order to connect.