Pickup location closed despite within opening hours

I tried to collect a parcel this afternoon at 4:30pm from the Gabriel Road Plumstead pickup location. I received an email earlier in the day informing me that my parcel was ready for collection and giving the opening times of that specific pickup location - until 5pm. I arrived and it was shut. There was a group of at least 6 of us wanting to collect, ringing the bell to no answer. All this despite it clearly saying on the door that they are supposed to be open. This is not great service at all!