Hi I have problem with locking on vauxha Astra 1.7cdti 54reg?

When I unlock the car the back door on pasanger side doesn't unlock,it make the noise like is unlocking but the door won't open,I change the locking mekanizem but still the same,the only way I can open is from inside bay grabbing the handl inside and outside at the same time,any answer plzz thankyou