The cell phone bluetooth needs to be on, and in "discoverable" mode, to pair it. This is in settings menu on phone somewhere. Then you must use the "Active Captain" app to pair, not the cell phone menu. This is different from how you pair the bluetooth to your car, for example.
Bluetooth is a function on the phone, and is not related to cell service or plan. I can use bluetooth fine for music even with no cell signal in the boonies. The Garmin bluetooth notification feature requires the AC application, and will not work without it. You may need to give the AC app "permission" to use bluetooth, depending on phone model. Check permissions.
I don't really want notifications, and don't want to have the AC app on all the time, so I disabled the feature.
"Alive without breath, as cold as death; never thirsty, ever drinking, all in mail never clinking."