Our neighbours from across the street, who moved in a month ago, are having a housewarming party in front of their house. I can see several other neighbours at the party, but we were not invited. I am surprised and a bit disappointed. Another neighbour did invite us for their "we have lived here five years" party a couple of weeks ago. As far as I can tell, all interaction went well that evening (although the neighbours from across the street were not present). How can I tell why the new neighbours might not have invited us?

It would seem unlikely that they already knew all the other neighbours closely before moving in.

I did already introduce myself as soon as they moved in and since then talked to them a couple of times. As far as I can tell, the interaction went well, but I might have missed subtle clues due to my Asperger's Syndrome.

Or maybe I'm overthinking this and they just wanted to keep the party not too large, and already had a positive interaction with those neighbours they did invite.

Region: Central Germany. To the best of my knowledge, all neighbours are culturally Germany.