Immobiliser

Hi, I have a problem with my immobiliser, when I unlock the car with the keyfob the car unlocks as it should and the immobiliser dis-arms, however when I get into the car the immobiliser arms itself and I have to press the unlock button before it will start, any help would be greatly appreciated.

The passive immobiliser kicks in due to unproper fob(rover 75/freelander 1 sold as being D2 by some ebayers) or passive remobilisation coil/circuit failure, open the fob and see if it has the pointed bit or not, if not it's not D2 fob and it will never work 100% OK unless you disable the passive immobiliser with tester

Thanks for the quick reply, the fob is the original one with a new battery. It only started doing after some heavy rain and before I sealed the sunroof