Hi Michael, sorry for the late reply.
Unfortunately blueman 2.1 has a buggy PIN database built-in that probably leads to a random 4-digit PIN getting provided in this case instead of the 0000 that the device expects.
However, the database is not part of blueman 2.3 anymore, so I would expect the PIN code request to show up in testing. In case it does not, please see https://github.com/blueman-project/blueman/wiki/Troubleshooting#debugging-blueman on debug logging and check what you get with it when trying to pair the device.
Cheers
