I personally have on two separate playthroughs completely maxed out the sex shop (at least, so far as I can tell) and proceeded with Cara's story until there's just repeating event left with your aunt. Gabrielle is also being blackmailed at this point. Never have I seen the strip club go under, at least not that I'm aware of.
Either there's another trigger, or there's some kind of time constraint.
Don't employ any of the non mandatory characters like your mother or sister until you've gone through all their taboo breaking events or they can bug and be impossible to complete the quests. This doesn't let you out of sex scenes, but can interfere with meeting other characters or storylines. For example, I've never had Erica Davenport's love scenes start and on one playthrough I never met Iris Vandenburg, who is completely useless, but still.
You also shouldn't rush ahead too quickly with raising sluttiness and love or it can break progression.
Sluttiness raises for sex acts when the girl orgasms, but there's a cap to how high it can raise by doing so. Once you hit that cap, you need to go up a tier in sex acts. Fingering will get you started, then cunnilingus, and then when you have permaboner you can more easily raise sluttiness via sex itself. But by that point you don't really need to.
Your mom becomes your secretary. I believe it interferes with event progression if you do it too early and she doesn't really do anything at work except give a few optional sex scenes. It gives an alternative way to break her taboos, though, because you can just say "You work for me, imma fuck you now."
Ashley unlocks once you've progressed far enough with your business and once you're close enough with Steph. She's important to max out because she boosts your energy recovery and lets you have a permaboner.
Also, it was already mentioned, but when making your first serum you don't really want to load it up with effects or anything unless you're cheating your money. Lots of traits add lots of attention to the design, which can call someone in who will waste a few of your time slots and possibly add even higher attention to the drug by making it illegal or confiscate money, the drugs themselves or the design of the drug. You can seduce her and get her to knock it off and other useful things, but doing so takes some effort because her love starts in the negatives.
It's just on a cooldown and not really necessary for her progression afaik. You can blackmail her into sex and stuff, which is a way of getting around the fact that she's meant to be a low love/high lust character, but lust is difficult to progress without love. Once lust or obedience get high enough it basically stops mattering, but it's useful until then.
Basically, don't worry about it. Just focus on getting her lust and obedience up, which is pretty easy after awhile, especially when you unlock auras.
