I meet somebody almost every day of the week that used to be my friend. Maybe he still is because there was no falling out or anything like that. Things changed completely after he got married. There were a few times he had asked me to call to his place but when I'd ring or text on the day he'd tell me not to with something vague for an excuse. I never got any bad vibes from his missus but I'm guessing she doesn't like me. It hurts a bit but I can understand it. It may even be more unfair on him than me really.
Shit happens, things change and you just carry on. I'd still be there for him - or them - in an emergency, if I was asked for help or even a favour. I haven't forgotten the past and won't either.
I don't have a relationship with anybody else that comes even close to the friendship we had so sometimes I feel the loss badly. But that's just part of getting older anyway.