Hard to give some advice from a single image only (There seem to redundant/offset surfaces due to (CT?) scanning errors but all I know about the shapes of orbital bones is based on some quick and dirty googling).
So just some technical info about repairing holes:
"Holes" in terms of MM are defined by open boundaries > The surface isn't watertight. This is a MM "hole":
To each such single open boundary (indicated by blue markers) ANALYSIS/Inspector on AutoRepairAll adds a filling surface. If there are several such holes this might result in infills intersecting other surfaces.
Instead of running AutoRepairAll in Inspector you can also click on the marker spheres one by one to close the corresponding holes one by one (If such a infill doesn't give an acceptable result undo it via Actions menu). Note the option to set the HoleFillMode to SmoothFill. This tries to create an infill based on the curvature of the surrounding area.
There's another tool to fill such single boundary holes: SELECT/Edit/EraseAndFill. Basically it does the same as Inspector but gives better control of the infill's curvature via its Bulge and Scale sliders. To use it you need to select the faces at an open boundary by double clicking right at the open boundary with a small brush in SELECT. Such a boundary selection looks like:

Now run Edit/EraseAndFill and adjust Bulge and Scale if needed:

So far ad simple holes.
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This is labeled as a hole by many users too:
A doubled sided surface where one drilled a hole in. There's no open boundary so it's not a hole in MM's terms.

To close such a hole you need to get rid of the surface connecting the interior and exterior. SELECT it:

And discard it. SELECT the interior open boundary:
And do EraseAndFill as we did above. Do the same on the exterior open boundary.
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There might be a case where you need to connect two non connected surfaces. As Inspector would create an infill for each boundary you can't use it in this case (if you don't build a Bridge between the surfaces to get a single open boundary). Here SELECT/Edit/Join is the right tool. In SELECT double click on boundary A and on boundary B :
Now run Edit/Join:

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Basically this should allow to fix all your "holes". Maybe there are still other issues?