Question

If there is no change in concentrations why is the equilibrium state considered dynamic

Answer 1

At dynamic equilibrium, reactants are converted to products and products are converted to reactants at an equal and constant rate.  Reactions do not necessarily—and most often do not—end up with equal concentrations. Equilibrium is the state of equal, opposite rates, not equal concentrations.
The equilibrium constant does not indicate whether a reaction is in static or dynamic equilibrium because it is simply the concentrations of the products divided by the concentrations of the reactants. A reaction is at dynamic equilibrium if the rate of the forward reaction is equal to the rate of the reverse reaction.