You might find your answer here Description in the 'save' and 'save as' dialog box disappeared. or how do i get the description back at the part level? just upgraded to sw16 and office 16 .
I haven't tried the "sldpropertyhandler.dll" out yet, but 1 of 3 computers at work is having the same problem you described and I hope this might fix it, though we are still on SW15.
The sldpropertyhandler.dll method worked. Thank you! I wonder if an update unregistered the dll?
Run Command Prompt (cmd.exe) (make sure you run it as an administrator). Type: regsvr32 "C:\Program Files\SolidWorks Corp\SolidWorks\sldpropertyhandler.dll"" (or whatever the file path to your "sldpropertyhandler.dll" file may be)
I just tried this and it worked for me too! Awesome.
My boss was worried I would take forever to fix it and/or break his computer.
'Nah 5 minutes' I told him and did it in 2:35.
I'll never know why it stopped working, but I can fix it now!