I really struggle here, I'm starting to think it's a SP.

Just one example:

One girl I've been texting, we have very sexual conversations - every thing is about sex. But it's lacking attraction, there's no sexual tension there. No feeling that "yeah this girls defo into me". There are some IOIs but she could just be a flirt after all.

This happens all the time, I make it sexual but attractions missing, tension is missing. Do I need to make the conversation about us having sex, or just sex in general? I usually keep it just sex in general, I try to get girls fetishes/favourite positions out of them and we talk about those. Good/bad?

My game's all natural but willing to try some canned shit. Need some help with attraction and sexual tension building.

Cheers bros.

Dude if you feel like it's going nowhere then make your intention clear. Do these girls know you like them? Are they getting your drift? If not then stop sucking up to them and stick to your frame of "I wanna fuck you, either you're in or you're out". Attraction is built by being a leader and being confidence and being congruent. If you state your intentions and don't apologize for them she's either gonna walk away or walk into your frame. If she walks away, then let her go. If she walks into your frame then it's on.

If they know you like them and are flirting with you but going nowhere, cut contact, it's a time waster. They actually have the upper hand here, not you. Find good leads, that's your job. there are girls out there who will fuck you. Find them.