Can't get this model to slice

[dwatrous]

Hi,

I designed a model in blender and have tried many ways and two slicers to get it to print correctly on my ender 3. I have tried Cura 4.7.1 and Creality slicer 1.2.3. In both cases, there is a big hole in the top that I can't close, and it seems to be printing something solid in the middle.

I did try using the 3D print toolbox in blender to Make Manifold, which broke a few things that I can't see how to fix.

I'm going to keep trying things, but I wanted to see if anyone in this forum had some pointers. This is my first 3D printer and my 7th print, so I'm learning fast.

Thanks.