My daughter gets up at 6-6:30 in the morning. She won't take naps anymore and she only falls asleep at 11 pm. I've tried all I know and have no solution. She's only 2.
Since the question is a bit vague, I'm going to give a vague answer.
I would do three things:
1. Get rid of any distractions
One big mistake I made early on, was to assume that my kids, who screamed a lot, would be able to fall asleep watching TV. It was not the case. I think my kids could stay up for weeks if I left the TV on. We have to make sure that they have no screen time of any kind several hours before bed time, for them to sleep. There have been several studies on TV/Phone/Computer time being detrimental to bed time.
2. Prepare for bed time
Sometimes if the kids aren't tired, it's because they didn't do much that day (which makes sense.) We try to make sure our kids have a good day, and have some exercise (without over stimulating), but we try to make sure that the stimulation ends well before bed time. They need a cool down period.
3. Don't give in
I've had friends complain about this before, and they would say things like "I lay my kid down, and they get back up, and we go and play for a few more hours, but every time I lay him/her down, they just get back up, and I go play with them". I don't know what's happening with your child, but when it's time to lay down and go to sleep, make sure they aren't getting up and playing a lot. I'm not saying to hold the kid down obviously. But if you get excited and go play with them every time they get up, they're just getting rewarded for getting up.
I'd love more information, to give a better answer, but this is what I have for now.