CDJ 900 HID mode not working

Hiya. 

I use Traktor in HID mode, the bar I play regularly always has CDJ900's but one of them has stopped connecting to Traktor. When I select Link and then press to connect it connects to my computer and says it's connected, but the next menu giving me the option to select the Traktor Deck doesn't come up, so I can't connect it to my Traktor to use it as a controller.

Is this a software fault with the CDJ900? the other players connect fine, it's just this one CDJ. It's happened a couple of other times in some other bars too, just wondering if there's an easy fix for it when this happens.