It's because of your bootloader. If you would have done a simple search for "wifi fix" you would have found various topics on this and how to fix.
Flash the modded bootoader via Odin (no knox) or flash to latest official rom (will enable knox).
Galaxy Note II | CM11 (Unofficial)
Nexus 7 | CM 10.2
> HTC Universal >
HTC Touch HD
> HTC HD2 >
> Samsung Galaxy S2 > Samsung Galaxy Note II
Galaxy Tab 7.0
> Nexus 7