Topology optimization

Hi to all,

Recently I have been working on topology optimization. The model has no error and shows the results of 0th iteration. However, after the 0th iteration, it can not continue to further iterations. We had similar issues, but when we changed the initial material fraction of the model, the problem was solved. On the other hand, for new parameters, the iterations are stuck at 0th. Therefore, what is the issue of my model? If you can give some ideas, I would be appreciated it. 

Best.