[DGJ]

Sometimes its a very simple fix. as mentioned above the antenna is a circle that's glued inside the plastic housing around the ignition switch. it needs to be close to the key to recognize it, and sometimes the glue fails and the round antenna just drops a few CMs inside the plastic housing. Just remove the two bolts and make sure it's secured inside the rim. if it's not, then glue it back in place.

No lie this has happened to me and it was such a headache to figure out until someone pointed it to me.

 

[DGJ]

Also, have a look at this discussion :

Eobd and Immobiliser lights

The bike would not start after a refuel, When you turn on the ignition everything works but as soon as you hit the start button nothing happens. The eobd light stays on and the immobilizer led gives Two flashes and then stays on The immobilizer is disabled in the ECU, Voltage is good@13.4, fuel...

www.ducati.ms

Well, Rob, since you popped up, worth mentioning that if one installs a motogadget with your (extremely convenient) module, the ECU needs to be reflashed to remove the immobilizer.

Motogadget or not, depending on the circumstances, it's not a bad idea to get rid of the immo altogether, that way it could never fail.