Divergence VS Dimensions

Good Morning,
I performed different simulations of flat coils to see the magnetic flux density without any error and results look reasonable.
The problem is that when I reduce the size of the flat coil (Diameter=30 [mm] , wire diameter=1 [mm]), and choose a finer mesh, Comsol fails to find a solution:

Failed to find a solution.
Divergence of the linear iterations.
Returned solution is not converged.

I am using Magnetic Fields physic. Should I use a different physic for very small devices?
Is the divergence because of the very small size?

Thanks,
Nima.