Surface Pro keyboard functions no longer active

[Surface100]

Hi, the function keys on my type cover 2 (e.g. changing the keyboard brightness) no longer work unless I hold down the Fn key. Whereas before I never needed to hold down the Fn key for them to work, and now when I press them without the Fn key they only work as traditional function keys (e.g. F1 - F12). I know this is not a problem with Windows 8 as when I boot into the Bios settings I still have to hold down Fn to get the functions to work. Is there a key combination I have to hold down or something to get it back to the default like it used to be, so I no longer have to keep holding down the Fn key when I want to use the functions. Any help will be much appreciated.
Thank you

 

[Metalman]

Yes, hold down Fn then hit Caps. That is how you turn it on and off.