Well try turning the wii on plugging it into the wii and leave it charge or if it runs on batteries returning the batteries and if that dont work return it to the store for being faulty! please rep me ++ if this helped!
Had the same problem. It's a sync problem.
First, best to double check you have fresh batteries.
Next, turn the board upside down and remove the cover from the battery compartment.
Open the small hatch cover on the front of your console unit.
Now start wii fit from the disk menu item.
Next, press the small red button inside the balance board battery compartment. The blue lights will blink for approx 3=5 sec.
While they are blinking, press the red button on the console (in the hatch compartment).
This should re-sync your board and the light stays lit.