TLDR; looking for books on how to follow up from a first date/lay

Most PUA books seem to mainly focus on generating leads, escalating to sex, without much talk about what to do after (correct me if I'm just blind). Do you fellas have any good recommendations for how to handle the after-sex part??

Context: Met a girl who I met at a party and had crazy chemistry with at a party, we went on a date and were touchy and made out. She was on her period but wanted to meet up 2 days later for sex (she was very open and forward). Fast forward 2 days when I follow up, she sends a text saying that I'm "a lovely person but unfortunately not quite what I'm looking for in a dating/relationship/romantic partner."
(I've asked for feedback, but she hasn't read my response yet, will update thread when I do)

A bit of background: I'm 37, just got out of an 8 year monogamous relationship last year, and have worked really hard this year to take control of my dating life. I feel a huge shift in mindset and notice the new ease I have with interacting with hotter and hotter girls. I'm currently trying to build a poly/casual rotation while I work on personal projects.

Initially, getting over approach anxiety took WAYYYYY too long, and stopped me from gaining XP with all the other skills. I couldn't make any progress if I didn't have any promising leads to follow up on!
Now that I'm no longer having trouble approaching, connecting, texting, getting dates, getting laid, I'm running into a new problem --
Most of the time I'm getting friendzoned afterward. I'm having trouble figuring out if it's a cultural thing (I live in NZ, people seem pretty commitment phobic generally), if I'm giving off too intense vibes (because I got used to interactions with my ex-GF), if I'm too chill and not passionate enough, if I'm not conveying my intentions early enough, or if this is just part of The Game and most people are gonna be incompatible and I need to just suck it up and keep getting better. Maybe it's just bad/incompatible kissing and sex, but I'm working on that too!