First post on here, please be nice…
I had exactly the same issue today with my Xperia Z3 Compact, asking for a PIN for bluetooth pairing. I tried all combinations of four, five and eight zeros, 1234, 12345 etc, but to no avail. I also tried rebooting the phone and resetting the Mooshimeter, no joy. This meter is known to work with a Samsung S7 and a Tab 3, so no hardware issues on Mooshi’s side.
The eventual cure was to connect the bluetooth from the Android settings in the phone before selecting the meter within the Mooshimeter app, first go, perfect.
Hopefully this helps someone out there hoping to, like me, devote a pensioned off phone to a more technical life!
Regards,
Scott.