Hi MarkOfChain (excellent username),
Just thinking out loud… if you can connect with other devices, we know it’s not a hardware problem with the meters. Can you provide the model of the Android 6.0 phone that’s having trouble?
The first thing I would try is to reboot the phone. Then try connecting with wifi off (wifi and BLE interfere on some Android phones)
Another Android bug that has bitten users is that sometimes the phone “bonds” to the Mooshimeter (you might see a pin code request), and the bond is saved to the phone. The Mooshimeter does not support bonding, so inconsistent behavior results. You can see if this has happened by going to settings->bluetooth and looking at the bonded devices.
If none of these solutions work please let me know (along with more details about your phone itself) and I’ll try to provide other options.