Are there rules for selecting a BLE device address

[DS.4]

One of the addresses we selected for the device appeared as not connectable on android scan.

[Hdd]

It depends on your specific use case and application, but in general :

• The address must be unique.
• The address must be random.
• The address must be valid (following the format specified by the Bluetooth SIG).
• The address must be non-resolvable.
• The address must be public or private.
• The address must be unique within a network.
• The address must be easy to remember.

I think you need to check the device's advertising configuration, the unique address and its type (public or private), the RF part if it's correct, etc.