I cannot enter the children's arts tax credit for my child. I have entered it for my other two children but for my oldest, the boxes are locked. I cannot type in them?

I click on the the edit credits on the dependents screen. I can enter a fitness credit for her and I can enter the arts credit for my other 2 children but for some reason, the boxes are locked at 0.00 and will not allow me to click and enter an arts credit for my oldest.