Bad luck
I guess the moral is not to drop a Gemini! Though I realise that's not a lot of help to you right now...
I don't know where the wifi antenna is in the Gemini. If you've knocked that loose, there may be a small chance you might replace it yourself. (You could look under the plate behind the screen. Though my guess would be at one end, under the plastic end cheek, which could be a lot harder to get to.)
Otherwise, there's probably not a lot you can do other than send it for repair. (Talk to Planet Computers; I gather they're pretty helpful. I don't know of anyone else repairing them.)