Debian requires a passkey-agent to run, instead of the pinhelper app, which used to be used before.
Thus if you want to make a bluetooth connection and for instance pair with your phone, you need to have this agent running to monitor outgoing pin requests.
A passkey-agent comes with the bluez-utils package, but it's not compiled.
It's in the /usr/share/doc/bluez-utils/examples/ directory. Cd to it, unzip the passkey-agent.c file and compile it. Put the resultant passkey-agent file somewhere in your path.
Now, before making a connection to your phone, run the passkey-agent by:
| $ passkey-agent —default 12345 |
Then you can connect to and pair with your phone. If you then authorize the computer on the phone to connect without confirmation, you do not have to run passkey-agent before connecting again.
Finally, kill passkey-agent by:
| $ sudo killall passkey-agent |