Hey, IF there is a fault in the immobilizer system; that is why your car won't start and the light is flashing. There are a number of possible reasons why the immo is coming on; to diagnose the problem, it is best to start with a Volkswagen specific scanner... see if there are any trouble codes.
To understand how the system works and what to look for, to troubleshoot the problems... check this website (join the website; to get further access, to member only information):
Immobilizer FAQ and troubleshooting for VW and Audi, with key replacement tips | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum
If you can get your car scanned for trouble codes; please post them here, we will go from there!
To understand how the system works and what to look for, to troubleshoot the problems... check this website (join the website; to get further access, to member only information):
Immobilizer FAQ and troubleshooting for VW and Audi, with key replacement tips | VW TDI forum, Audi, Porsche, and Chevy Cruze diesel forum
If you can get your car scanned for trouble codes; please post them here, we will go from there!