I think the best step-by-step solution for this problem is already available in the following forum post: https://forum.ansys.com/forums/topic/error-inside-ansys-ls-dyna-an-error-occurred-inside-the-solver-module-general-error/
I'd the same problem with our license and solved it following that process. Also, after installing, double check if your license server is properly defined.
I hope it helps