My DP is a lot like yours @Whackamole11 , had never orgasmed before she met me, and that continued to be the case for the first 17 years of our relationship. As a result, while she does enjoy the sensations involved in sex, it's also an exercise in frustration for her, as she gets close and then it just gets too much.
As a result she also never masturbated, as what was the point. Shed tried it when she was younger, but she lived in quite a chaotic house growing up, so didn't have a lot of opportunity, and I don't know if that had any bearing on why she never discovered how to orgasm, or whether it was a physical thing. Who knows.
Anyway, I was much like you. Wanted to be the one who could do that for her, to let her feel something that I considered a pretty vital part of life. Like you, I tried different techniques, toys etc, but nothing worked.
After a few years, I accepted it wasn't going to happen, so I stopped focusing on it. And that actually improved our sex life. Instead of focussing on the destination, I learnt better what she enjoyed about the journey, how to keep her at the point before it got "too much", and so minimise her frustration.
It sounds like you're on that track now OP. You mention your DP likes massage, my DP likes to have her body stroked. Her back, her arms, ears, back of her neck etc. I learnt to see this as sex, it includes the closeness, the physical touch, the intimacy, just not the genitals. And often,that stroking will lead to "proper" sex, but for DP to enjoy the stroking, then it needs to come without the expectation that sex has to follow.
Secondly, you have this idea in your head that your partner doesn't enjoy sex. You have absolutely no idea if that's true right now. You need to talk to her about it. I've felt the same at times but it's not true, at least not for my DP. She found sex frustrating, but the actual physical sensations, she enjoyed, right up until the moment she didn't. She's not asexual, she gets turned on, she enjoys giving as much as recieving, and she enjoys the feeling of PIV and of me orgasming. She enjoys the intimacy and closeness. She just didn't enjoy the feeling of pain that came where an orgasm should.
Your really need to communicate with your partner, no matter how difficult and awkward it is, work out what your sex life can look like, because at the moment you're just assuming,without her input.
And finally, just to give you some hope. Last year, at the age of 43, 17 years into our relationship, DP had her first orgasm. She entered perimenopause last year and it has changed something. We weren't doing anything special, nothing new, and then bang, earth shattering orgasm. Since then, theres been no stopping her. The frequency we're having sex has increased dramatically, quite frankly I can't keep up!