q vxB magnetic force

there is something I don't understand
maybe someone can tell me

- a charge q has velocity v along the x axis
- there is a uniform magnetic field B along the y axis
- so the particule experience a force F=qvB along the z axis

Now consider the same situation in a reference frame moving at velocity v along the x axis.
Now F=qvB=0 and there is no force on the particule.

What am I missing?
How to reconcile those situation?