Wearing acrylic nails in your nails prevents water of Wudhu or Ghusl from reaching to your real nails, hence invalidates your Wudhu and Ghusl. If you wear it after performing Wudhu or Ghusl then pray Salah, your Salah will be valid because your Wudhu or Ghusl were valid as you performed Wudhu or Ghusl with out wearing anything stops water from reaching to your nails.
Wassalam.