nPlease describe the loads and supports on the shell.nIf there is a pressure on the convex side or a large compressive load in the membrane direction of the shell, then the reason for the lack of convergence could be due to the load approaching a buckling load. That can be a reason why a Static Structural model will converge with Large Deflection turned off, but will fail to converge with Large Deflection turned on. The structure becomes unstable as the load approaches the instability. With stabilization or arc-length methods, the solution can proceed past the critical load and show post-buckled results.nBuckling can also be mesh dependent, and we see some evidence of that since the coarse mesh got a little further than the fine mesh.n