Question
Drawing recovery manager on the Mac platform not working especially after applying some updates.
Answer
This seems to be a known issue (the drawingrecovery command yields a null response)
If this is the case you need to manually rename 'bak' files or 'SV$' (temporary save files) to the DWG format.
Refer to the list of 'missing' AutoCAD functions with the Mac platform on a separate FAQ.