System Preferences Grayed out

Also boot into Safe Mode, Mac OS X: Starting up in Safe Mode, and try from there. If successful reboot normally and test again.

Note: the Safe Mode boot will be more lengthy than normal as the system is doing some self cleaning and repair.

Create a fresh user account and test to see if it works as expected in that user.

macOS Sierra: Set up users, guests, and groups on your Mac

Enter in user library macOS Sierra: Library folder

Find a folder preferences - delete com.apple.systempreferences.plist into the trash .

Then restart the Mac and empty the trash , open safari and browse for some time .

You're welcome. Glad it's sorted.