Guy's Behavior

Why would a guy who likes me not accept my follow request on instagram or follow me back?

There’s a guy I like & I think he likes me back. We had this thing going on for about a year & a half where we both really liked each other but we barely talked. I was too shy to talk to him. However by the end of the year I decided to request him. We were both seniors & were about to graduate so I decided to request him. The next day it seemed like he wanted to talk to me cause as I saw him looking back at me smiling. However my anxiety got the best of me and I looked away and backed down. I ended up deleting the follow request. A whole year later I saw him at the high school we graduated from and he started talking to a guy friend I was with. He saw that I was anxious so he started talking to me. He asked me how I’ve been which I said “good”. It looked like he got sad cause I only said one word however I was anxious. We ended up leaving and as he said goodbye to my friend, he kept smiling and laughing at me cause he knew I was nervous. I think he thought it was cute. About a week later I saw him on a date with this girl. He looked nervous when I caught him cause he got sad and looked around. I just ignored him. Then days later I go on his Instagram to see how he’s been and I see he looks depressed heartbroken. I normally can tell when he’s sad. Then months later I look at his pic in August he looked DEPRESSSED. I got scared cause I thought he could commit suicide. So I decided to message him cause I knew it would make him happy. As I texted him it took him TWO DAYS to see it and respond but when he did he seemed really happy. Just then I saw a new pic he posted of himself the day I messaged him. He looked SUPER HAPPY. So I waited 3 weeks for him to message me back but he didn’t so I initiated since he was the one who always initiated in the past which I usually ignored cause I was nervous. He ended up replying and conversing but then out of nowhere stopped so I unfollowed him again. It seemed like he like me so why didn’t he ever follow me back?
Why would a guy who likes me not accept my follow request on instagram or follow me back?
Post Opinion