Central locking has suddenly stopped working :( ?

Hi guys Can you help ? I have a very old polo (2001) fitted with an old laser line 211 modular alarm The car has central locking that works with the fob or shall we say it did! The other morning when I got to the car the doors were open I got in and the alarm went off It seems when I pressed the button on the fob the night before the alarm had activated but not locked the doors Infont know if I've pressed one of the other two buttons causing the locks to be key activated only Any ideas thanks in advance Kim