I am trying to solve the nonlinear analysis in ansys student software(18.2). When I use commands to extract element stiffness matrix, I encounter with, " An unknown error occurred during solution. Check the Solver output on the solution information object for possible causes". This message is constantly displayed. When I have checked the solution information, it doesn't show any errors. But in the solution tab in the information section, it shows " solve required". Does this means something? I am attaching the screenshot of the same for the reference. Please look after the issue.