1999 Volkswagen Van alarm problem

Ive been on holiday for a week and left my van with the alarm on during the week.
to set the alarm theres a fob that presses into the dash onto the contacts, theres no batterey in the fob.(Checked that first)
getting into the van the alarm went off, (normal) but the alarm wouldnt turn off, started the engine a couple of times but then the immobiliser kicked in so wont start at all. Disconnected the battery because of noise.

cleaned the contacts and tried again and still no good.
any help would be much appreciated as I need the van for work.