I have a part that is shelled, and when trying to run a nonlinear study, I get an error saying "Solution Failure in the first step". I feel like the problem is due to: "1. Lack of adequate fixtures...", but I am not sure how to fix this problem. I initially tried a solid mesh, but the tank is too thin. I also tried just making the tall section shelled and the rest a regular mesh, but it looks like you can not mix mesh within a part.