How do I make friends as an adult ?

I’ve always struggled with making friends because of my autism and ADHD. The confusing part is that when people actually get to know me, they usually tell me I’m a nice person and fun to be around. I’ve even overheard people saying positive things about me. Yet no one ever seems to stay in my life or want a closer friendship. It’s hard not to wonder what’s wrong with me when people seem to like you, but never stick around.