All I’ve done is create four circles, then push them up to create cylinders. Everything looks OK in Sketchup, I can’t tell what’s wrong, but clearly it’s those cylinders. Here’s a preview:
It will never be a solid until you add the missing face and remove the faceless edge, ]I also recommend that you delete the guides, although that’s optional].
It’s still not yet a solid.
SolidInspector² shows a nested group in one corner - select in the Outliner and explode it.
Then there are 14 surface border - i.e. edges without exactly 2 faces [probably around holes], and 104 internal face 'partitions. where some edges will have more than the 2 faces that are mandatory for a manifold solid.
So there’s still a lot to fix…
SolidInspector or SolidSolver cannot fix them.
Do it manually…
I suspect that starting again and keeping it simple would be the faster way forward !
The main form is actually quite simple - you seem to be making it more complicated than it needs to be.
It was suggested that you redraw or at least clean up this model when you first posted it. Unfortunately you didn’t and your additions to it are making it more difficult.