Disclaimer, I'm neurodivergent and officially over trying to respect social norms if they don't make sense. I'm well enough liked so it's working okay so far.

Just be the person you'd be if they were being friendly. They're not introducing themselves? Introduce yourself! They don't return the favor? Ask them questions! It's exhausting sometimes but if you break the ice it makes it easier for others to follow lead. Lead by example.

Same with your weirdo manager. "Whoa hi there hey! What's up!" Point out how effin weird he's being by just lurking without saying anything.

You're already doing it a bit. Some people just aren't good at meeting strangers and need a bit of help.

Unfortunately some stores just have a toxic vibe, and it pretty much always starts with the manager. There are things I could suggest you do, but they all basically require you to do extra work to try to lift the culture of your store out of the gutter…

Honestly I would just bide your time and look for another opportunity to transfer away. If you have the courage to do so, you could have a conversation with your manager or with your district manager about how you are feeling, but I don’t know if that will necessarily help much.