OK, between the battery and starter is a starter solenoid, normally listed in the ducati parts manual as "remote Switch". It has two large black cables going in to it and a white plug. check the cables first. if you hold the solenoid and hit the start button you should "feel" the click.

the dirty way to test the solenoid is to lay a spanner or screw driver across the two large contacts and if the motor spins its a dodgy solenoid. but first check ALL the conectors!

Chris