The MAC forum is way over here http://forums.autodesk.com/t5/autocad-for-mac/ct-p/3011, no one in this WIndows-users forum can help you.

The latest MacOS may not be fully supported with your old R2015 software, you might have to upgrade your AutoCAD for MAC software. Make sure all AutoCAD flr MAC 2015 updates are installed and see if that helps.

Now go ask in the correct forum.