The box isn’t printable because you haven’t got a solid component or group. Part of that is due to the way you have structured your model. You still haven’t done what I told you on Saturday.
Zoom in close on the holes in the box. The red void components extend out through the side of the box. They do that on the inside, too.
Your void components are still components. They need to be exploded so they become part of the box geometry. At this point explode ALL groups and components. Select all of the geometry and run Intersect Faces>With Model and erase the bits where the hole components pass through the vertical faces of the box. Then make a single group or component and ensure that Entity Info reports it as solid.
