Huge Build-Up but NO ORGASM

Hey guys, in a bit of a spot with no idea what's up. Never happened to me before. I've had girls that can get off VERY quickly, both from external and internal stimulation, clits, g-spots, even both at once. I've had a few girls that I just couldn't stimulate right, and even though it would feel good, it would not build up and would just be one of those "this feels good, but it's not getting any better, BUT it's better than nothing."

But what's happening now is neither. With both internal and external stimulation and rubbing, she builds up right to the point of orgasm, but just doesn't go over. She hikes the cliff but doesn't bungee jump off. Here's what happens, I'll give an example of clit stimulation.

1) I start rubbing. I know what makes her feel good, the feeling starts to build up. It starts off with gentle moaning and slow hip movement, she gets wet, then the moans get louder, she starts breathing faster.

2) I continue to rub, or go down and eat her out. Same thing happens, her hips start bucking, moans get louder/uncontrollable, and RIGHT when you'd expect her to orgasm, she either peaks out and stays at that level, balancing right on the edge of climax but not going over, or tells me to stop because it feels too good (compares it to tickling, where it feels good but you can't take much of it). I know the feeling, I sometimes will get it during head, but it goes way if she changes technique slightly.

The same thing happens when I finger her. It builds up like ANY girl, but right when she gets to the point where she's supposed to orgasm, she can't take any more of it.

I've held her down and kept on going before, but she STILL doesn't get an orgasm, she just kinda stays at that level and squirms around/bucks her hips, moans/screams loudly until I stop.

This isn't a call to what an orgasm's like, it's usually pretty routine to get a girl to orgasm. If a girl is unresponsive, I know I'm not doing something right. But this girl builds up EXACTLY like she's supposed to, but just doesn't get off.

What do I do???