Help please regarding key fob

I have a disco on a k plate all has been great now i have a small problem with the alarm fob (2 button) it has been locking and unlocking the doors and turning off the immobiliser as it should do but today it wont do anything apart from blink its light at me i have a seperate immobiliser fob which allows me to drive the car (luckily).
what could be the problem please help
thanks.
__________________

by the way i had to take the battery off a couple of days ago but it was working fine till today do i have to link it back up to the system if so how thanks again

Depending on what state the alarm/immobiliser was set at, eg alarm on or off when you changed the battery, you will need to reset the system.

I can't remember offhand how to reset the thing but I believe it's well covered in the owners manual.

I think it's a matter using the door key and turning so many times to the left and right depending on your alarm code.

Sorry I can't be more specific.

If the problem is in the handset, then there is a laid down procedure again in the handbook for reinitialising a handset.