Hi,
It's normal for Windows Defender to be disabled if Norton is installed in order to prevent potential conflicts.
Launch the Norton interface from its icon in the Taskbar and see if it shows that your system is protected.
If there is an error indicated, post back with the details.
If Norton shows your system is protected, try the following.
Hold down the Windows key and press R.
Into the Run box type regsvr32 /u WMIUTILS.DLL and hit enter. ( Include the spaces as shown )
Restart the notebook.
Again, hold down the Windows key and press R.
Into the Run Box type regsvr32 WMIUTILS.DLL and hit enter.
Restart the computer again and let Windows fully load for 5 minutes before checking the Action Centre.
Regards,
DP-K