Need help with stress simulations

So I have this frame, for a long-john type cargo bike.
I need some stress analysis performed on it of our design project to be complete.
I have tried everything and the opposite of it, yet whatever I do, once all the fixtures and loads are set and I tell the software to mesh the body and run the simulation, it fails after trying to mesh the body for a while.
I tried to add features to remove some of the failing edges, make the mesh size an order of magnitude smaller than any geometry I have in the frame, using different types of mesh, and still I get no noticeable improvement.
I'm pretty desperate at this point. Any help other than "go make another frame" would be most appreciated.
Frame is attached as a solid body.