Hi Paul,
What exactly do you have mapped to EXT1?
For example, I just mapped Source: mod wheel (CC1) to EXT1, and now when I send MIDI CC1 with value a of 127 as the tap source, I can tap in the tempo correctly and the LED on the front of the unit updates and flashes in time.
You should also confirm the exact MIDI message that is being sent from your controller. You want every press of the button to send a value of 64 or higher to trigger the tap.
