One thing I would say is not to "hyper fixate" on getting friends or thinking something is wrong with you. Lower your standards.
Maintaining a "close group" or a "tribe" isn't actually the overwhelming social norm.
Of course some people have a "girl gang" set up from school and enjoy it.
However, a lot of content, functional people don't have big social groups and thrive. The "Sex and the City" lifestyle is complete fiction for most women.
A lot of people say you "need" this super close group of people for support. Or in an emergency.
Often people find a regular social group isn't actually helpful in practical ways, and needs too much time and energy to maintain.
You'd be better having savings to pay for emergencies and being on speaking terms with 1-2 neighbours, or knowing what services to access locally.
(I'm ostenibly quite introverted but I have good judgement, I've learned "adulting" well. This seems to work much better than having a "bestie"!).
In my 40s many mainstream people are focussing on career or money or kids or relaxing at home time or their solo interests.
Many friendships are fairly situational and superficial. Maybe you share an office together and hit it off as you're the only two females the same age
Or you have a hobby for a time and spend time together during the hobby. You drift away after a time and thats Ok.
I don't think individual social skills actually count as much as people think.
People tolerate poor social skills from certain people and not others. If your "face doesn't fit" for any reason in a group you may be labelled awkward or annoying. Can be ND, can be other things. You might even be too pretty/normal looking/mainstream for the group!
Plus timing may be a factor.
I've met some super cool people with great social skills, I genuinely just don't have energy to stay in touch with them.
If you have the energy/desire to meet people naturally and genuinely enjoy it then go for it. People can be really great on an "ad hoc" level.
Similarly there's nothing wrong with preferring to stay in with family or talking online and being quiet at work (unless you're being bullied which is a seperate issue).
Don't ruminate or beat yourself up over saying or doing the right things. 99% of it is out of your control.