Pen tablets like the Intuos or Wacom Intuos Pro are connected to a computer over a USB cable and will show a power light on the tablet once connected.
If there is no power light on the tablet, make sure the tablet is connected directly to the computer, avoid using USB hubs, keyboard/monitor ports, or docking stations with the tablets, as they can cause inconsistent behavior. If the tablet has a wireless kit, remove the kit completely from the tablet and test again. If the tablet still does not receive power on, test with a new USB cable if able.
If the issue continues, contact Wacom support. Please have a copy of the sales receipt for the tablet available as it will be needed to validate the warranty for repair.