My HVAC equipment (diffusers, VAV boxes) is not showing up in plan view. They print most of the time and I can see them in iso view, in plan view I get a connection point and nothing else. Layer 0 is on and display by elevation is off.
It's possible their Plan view block is corrupted. I've run across this in support a few times.
Write down all the missing MvParts and their sizes.
Start a new empty file.
From your toolpalette, add new (Good Copies) of each missing MvPart.
Their good part definitions are now in this new file.
Open the bad file. Select All (Ctrl +A), Copt to clipboard (Ctrl +C).
Switch to the new file and paste (Ctrl +V).
The old parts will be forced to use the good definitions already in the new file.
At the command line, type in OBJRELUPDATE. This will refresh the model.
The parts should display in Plan now.
Don't forget to copy across any Paperspace objects.
Hope this helps.