Hello To everyone

I am in need of help desperately. My 1.8exi won't start as the immobilser won't let it, i think. The dealer say there are no fault codes showing and they suggest bringing it in when it plays up.
If i could do that i wouldn't have the problem!
Anyway does antone have any ideas as what is causing this as i'm stuck and the car is useless.

When it goes it's quite good
many thanks
Juan