Alarm key fob not working after changing batteries?

I just brought a golf vr6, need a bit of love but is a great buy, it needed the alarm fob batteries replaced, i manage to lock the car with the fob then went and replaced the batteries, but when i went back to the car i couldn't open it with the fob even though the light is working in the fob, i tried to start the car but has an immobiliser and even putting the fob in that i still cant start it the alrm jus goes off. I've tried disconnecting the batteries and other things but im getting no where has anyone had this problem? Its a 1997 vr6 highline

Do you have any idea what this could be? i hate immobilisers they always seem to go wrong, but the key fob light works but won't even open the doors so im not sure? it seem to turn the alarm of still once the alarm is going of thou :/

Any help appriciated thanks