Google Cloud Messaging / view & reverse engineer requests made from app

There is an app that my program works with that uses a GCM token in order to create a session (login) and something changed with it recently. I no longer know how they are generating the token variable that I need in order to make a successful request. Someone experienced with app sniffing with Charles Proxy/Fiddler/certificate pinning/MITM would be the best candidate for this. All I need to now is what request is being made so that I can replicate it within my own app in order to obtain the type of GCM token that is now required by their private api. The app is for iPhone and Android so if you can figure out what request is being made for either system or both, that would be great. We can discuss the app that I am sniffing via chat or something. Instant bids will be ignored. I want people to bid who know exactly what I'm trying to accomplish here.