Tan, my Izzy had been doing the same thing for a couple of weeks. I started doing what you say you're doing - lots of quiet cuddles with no lights and no stimulation. It didn't seem to be achieving anything except getting me very frustrated so I've just given in now if she seems to be wide awake and got her up for a couple of hours to play. She seems to be ready for bed a lot more quickly if I actually get her up and stimulate her, rather than try to keep her quiet when she really wants to be up (if that makes sense). We're still have a night or two a week where she will want a midnight play, but fortunately they seem to be easing.