You can bypass the immobiliser to get to a dealer by using the EKA code.
This enables you to enter a number stored in the BCU unit so that you can open the doors and start the engine.
The number is only available through a dealer, and they will require full documentation details from you, including the VIN number.
The method of entering the number is in the handbook.
When we 'lost' our key in a bonfire (don't ask!) we retrieved the key blade and had new keys cut. On entry to the vehicle, we had no alarms at all, but the battery had been off for a while when we did the engine rebuild. We were able to get it running with the EKA code. It is a one-shot method and once you turn off the ignition, it will reset itself after 5 minutes. If you leave the ignition turned on it will restart OK.
If you have suddenly 'lost' the ability to use the key fob, you may need to reset the system by disconnecting the battery for a while, depends on what the actual problem is.
Peter