This is a normal issue and something that we are aware of. Thankfully, it's an easy fix and nothing to be overly concerned with!
It is normal for one wheel to not spin when there is no load resistance. Once the non-spinning wheel is put under load or resistance it will start spinning. If something was wrong you would feel extra resistance in the non-spinning wheel when riding and you would notice that the board would tend to drift to that side constantly.
If you DO feel resistance from the wheel, please email firstname.lastname@example.org and we'll help you right away.