Guy started acting different with me?

Me and this guy at work used to joke with each other and have fun. But since September, he has become cold towards me for no reason. It's like we strangers or i did something to him. Like there is a room at work im in every morning and when he used to pass and he knows im there he would turn around saying "Good morning" very excited now he just passes without even looking at me. He is generally been like avoiding me not looking at me anymore. And when he does say Hello like today is like he dont want say it but forces himself to say it. Its bit hurtful because we were so close to each other now so distant and no no one said something bad about me he started behaving like this after i came back from vacation in September

Guy started acting different with me?
Post Opinion