Well firstly how did the mesh got to that point? It must be a crazy amount of polygons for Blender to complaint like that. How many polys do you have? Like 25 millions?I think the modifier goes up to level 6? It doesn't go any further than that. You can post a couple of screenshots to get a better visualization of the problem.
To Simplify you can either make a stroke with the detail level set very high or you can use a decimate modifier or even a remesh modifier or the normal remesh option.