If you have powered on your Airconsole, and the external Bluetooth dongle connected into the Airconsole USB-Serial cable is flashing blue, but from Get Console app you still cannot launch an "Serial Airconsole(BLE)" connection then read on
There are a couple of reasons why this can happen
1) Airconsole BLE can only be connected to 1 iOS device - if you have 2 iOS devices nearby both running Get Console app then might be connected to a different one (we get this in our lab a lot). Find the other iOS device and turn off its Bluetooth to force the BLE connection to drop.
2) If you have been using Airconsole on Windows or Android (via BT2.1) or have mistakenly tried to Pair with Airconsole in iOS via 2.1 then Airconsole's BT stack can get screwed up. After the 2.1 pairing attempt you will probably need to turn Bluetooth OFF then ON again on your iOS device, and also power cycle the Airconsole.
3) Cold starting the Get Console app at this time also can help - by double tapping home button and swiping up to completely close the app. Once the blue LED on the Airconsole bluetooth dongle is flashing again, enable Bluetooth on your iOS settings and then launch Get Console app again.
You should after 5-10 seconds see "Airconsole-XX detected via Bluetooth" come onto Get Console's terminal screen. If you are also connected to Airconsole's WIFI network then you might also see "Airconsole-XX detected via WIFI" before the Bluetooth announcement. Once you see that Bluetooth detection, the Quick connect dialog (Serial->Connect With: Airconsole(BLE)) should be green colour.
Hopefully that solves your issue