Thanks for your replying.
1、 My system is ubuntu 20.04, version pylith2.2.2 .
2、 I wanted to simulate how gravity would affect the interior of the lithosphere in areas with significant differences in topographic height.
I used a 2D model, quadrilateral mesh, and set the sides and bottom as free sliding boundaries, without considering faults .
3、 In my initial simulations, I used viscoelastic materials for the entire lithosphere. Yesterday I modified the crust to an elastic material, but the initial stress state is still given for the elastic material .
The simulation ran successfully after I removed the initial stress state for the elastic material.
Maybe I didn’t make myself clear. In that example, only the initial stress is specify for elastic materials, the initial stress and initial state are specify for viscoelastic materials 。
I set the initial stress and initial state because my entire model was viscoelastic, but after changing the crust to elastic, I still specified the initial stress and initial state. Then I delete the initial state, specify only the initial stress, and the simulation runs successfully 。