Our investigation has shown that running “CleanMyMac 3” app is a root cause for this issue. CleanMyMac 3 interferes with S.M.A.R.T. subsystem of OS X, so that even Apple’s Disk Utility can’t work properly, it reports “S.M.A.R.T. status: Not supported” for all drives when CleanMyMac 3 is running. Turn off CleanMyMac 3’s menu bar item until MacPaw will not fix this bug.

You can learn more about this issue here:
  1. CleanMyMac Support Forum > Solution: Cleanmymac 3 login item interferes with S.M.A.R.T
  2. CleanMyMac Support Forum > Got some SSD SMART bug from CleanMyMac 3
  3. Crucial SSDs Support Forum
  4. TRIM Enabler Support Forum
  5. Google