Weird friends

Hello, I'm close to someone who has this friend who wants to be friends with everyone he sees. My friend had already been friends with this guy for over a year and had sort of established a great relationship. Now there's a new person who came into their circle and it's like his friend doesn't want to hang out with him anymore. Every time he asks to hang out there's an excuse from his friend. I don't feel well, I'm tired, I'm depressed, I've been so busy but, they are friends on social media and consoles like Xbox. He sees that while his friend is making all these excuses he's been hanging out with his other friend. There have also been times when he's messaged his friend and his friend checked the message but didn't message him back. His friend tries to tell him he's overthinking things and he needs to relax and then he tries to do and say things to make him feel happy, special, and non-suspecting but, the same thing keeps happening. No, he's not the kind of person to get upset when his friends meet new people he just doesn't want to be lied to, and just asking his friends has given him no results. He's asked me about it but I'm not that helpful because automatically I'd say that his friend is trying to avoid him. What can he do?