Well, I rebinded it to F12 since it's not used in game atm.(Except for "Switch to Seat 12") I think that the Overlay should be "enabled" by default or you'll have lots of people complaining about the same problem.
Edit: I'm pretty sure in order for the Overlay to show up properly, you have to start Recursion and enable the Overlay before you launch Planetside. Maybe you actually have to start a session too.