Door won't open when unlocked
2014 Vauxhall Astra 1.6 SRI

Does the door not open from inside or outside ?

If the button rises , the actuator for the lock must be working . This would suggest there is a fault with the lock mechanism / linkage which may be sticking . Unfortunately to check it out means removing door trim , awkward when unable to open the door . Often a good soaking with the likes of WD40 and operating a few times is all that is needed . Could gently try helping the button up / down by hand whilst unlocking . If you do get it open , check child lock not in operation .