This was advice I got. Worked for me.
1. Start the iRig BlueBoard device in native mode (while pressing the A button) and open the BlueBoard app. Make sure all other devices which use Bluetooth and have connected with the iRig BlueBoard device before are powered off (Or Bluetooth is powered off)
2. Select “Click here to connect” and let us know if the iRig BlueBoard appears here.
3. If your device does not appear, while the BlueBoard app is searching for the device, open a Finder window and go to the Utility folder to find your Audio MIDI Setup.
4. Inside this window, select MIDI Studio and Open Bluetooth Configuration.
5. Power on your iRig BlueBoard holding the B or C pads. This should trigger the iRig BlueBoard to appear in your Bluetooth configuration window. This will start the device in a MIDI over Bluetooth configuration. This will kick-start macOS to 'see' your iRig BlueBoard device.
6. Once recognized here, connect your device in the Bluetooth Configuration window.
7. Go back to the iRig BlueBoard app and power on your device holding the A pad to go back to native mode. Led will be flashing looking for bluetooth connection.
8. Start up BlueBoard app, should now see BlueBoard.
Now start up Blueboard in Native mode with A button pressed, then start Blueboard App. Works every time.