Just wanted to share how I solved my problem with the bluetooth pairing of my ASUS smartphone running on Android 7 with my 2016 Mitsubishi ASX. The steps shown on the manual for Registering a device with the automatically assigned Passkey 1234 did not work for me. I kept getting "Can't communicate with Handsfree System" on my phone after it failed to give me the screen to input the Passkey given by the car's bluetooth 2.0 interface in order to pair it. So, I tried the following steps:
1.Press the SPEECH button.
2. Say “Setup”.
3. Say “Pairing options.”
4. The voice guide will say “Select one of the following: pair, edit, delete, or list.” Say “Pair.”
5. The voice guide will say “Please say a 4-digit pairing code.” Say a 4-digit number. - "0000"
When the confirmation function is on, the system will confirm whether the number said is acceptable. Answer “Yes.”

When this is done, then go through the Reigster a Device process. This time, my phone connected straightaway to the car without even prompting me to enter the passkey or confirm pairing.

Hope this will help someone out who may be having the same problem as I did!