fridge door alarm

this fridge door alarm doesn't work properly. it is supposed to be off but in 20 seconds but it doesn't turn off .

Check that the timing IC works.
You may have to swap the capacitor C1.
It looks like that the timing oscillator doesn't start hence the continuous alarm.

Did it work previously ?

Verify the polarity of diodes D1 and D2 is correct.

Does the buzzer actually sound.

I don't think the piezo buzzer will reliably work of such a low voltage. It might work with new 3V batteries but once the batteries have discharged to about 2.4V the piezo will only get 1.8V as it's being powered from an emitter follower.