Contact between sphere and block

Hi,

Eventually i want to calculate the friction between a sphere and a magnet. To understand how contacts work in COMSOL i made two identical models, one which is 2D axisymmetric and the other one 3D. In the axisymmetric model i get the contact pairs to work but i can't reproduce these results in the 3D model although everything is the same. I get the following error:

Failed to find a solution.
Maximum number of segregated iterations reached.
In segregated group 1:
There was an error message from the linear solver.
The relative error (1e+003) is greater than the relative tolerance.
Returned solution is not converged.

Is there any difference between axisymmetric and 3D that i am forgetting?

I attached both the models.

Thanks in advance,

Janeau