Most hoverboard issues can be fixed with a simple reset.
In order to reset or recalibrate your hoverboard, you need to make sure your hoverboard is turned off and it's sitting level with the ground on its wheels. 
Without moving your hoverboard, press and hold the power button for 10 seconds. Ignore all flashing lights and beeps in this 10 seconds.
Then let go of the power button and turn the hoverboard off.
The hoverboard is now reset and ready to be turned on.
If this does not fix your issue on the first attempt please try a second time.