I just had a AC M do this to me last week. I had to default the AP and set it up fresh.
Different blue flashing patterns mean different things...
[Link: help.ubnt.com]If it's flashing 1/sec then it's more likely the BLE mode. I've setup cloud keys via BT but never an AP. Again I'd reset and start over
BTW uplink connectivity monitor just pings either the default gateway (default) or a custom IP address to see if that host is up. If the ping fails, the APs will stop broadcasting the SSID.