I am pay child support and I have been for a while now but every time I contact my ex partner to see the child she just doesn't repond. Plus I know the child is living with her nan and not her mom?

I don't see my child as my ex partner won't let me but I'm still paying child support. Why is this? My child doesn't even live with her mother she lives with her nan

You have to pay whatever the court ordered, and if you aren't allowed to see your child, you have to go back to court to have them order visitation or enforce what was arranged before. Countless people stop support when not able to see the child, of course, to force the other person's hand, but that's not the correct answer here.