IOS Google Analytics - no data coming through

I have 2 iOS apps that I am trying to connect to Google Analytics. One of them works, the other does not!

The one that works has been published for a couple of years now. The one that doesn't work is a new app, but uses the same code - just different graphics and data.

In the log, the only difference I can see is (the app that works):

INFO: GoogleAnalytics 3.10 -[GAIBatchingDispatcher didSendHits:response:data:error:]
(GAIBatchingDispatcher.m:208): Hit(s) dispatched: HTTP status 200

      

        
        
        
      

    

The app that doesn't work shows:

INFO: GoogleAnalytics 3.10 -[GAIBatchingDispatcher didSendHits:response:data:error:]
(GAIBatchingDispatcher.m:208): Hit(s) dispatched: HTTP status -1

      

        
        
        
      

    

As far as I can tell, the setup on the GA side is identical and both applications use the same files for the code. Also, the request seems to be the same except for the app id and UA key, which are correct:

VERBOSE: GoogleAnalytics 3.10 -[GAIBatchingDispatcher persist:]
(GAIBatchingDispatcher.m:497): Saved hit: {
parameters =     {
    "&_crc" = 0;
    "&_u" = ".etno";
    "&_v" = "mi3.1.0";
    "&a" = 53345067;
    "&aid" = "com.mycompany.myapp";
    "&an" = Recipes;
    "&av" = "2.2";
    "&cd" = Recipes;
    "&cid" = "f2da689b-ebdb-4e9e-9370-b8150c9950f1";
    "&ds" = app;
    "&sr" = 320x568;
    "&t" = appview;
    "&tid" = "UA-56722604-1";
    "&ul" = "en-gb";
    "&v" = 1;
    "&z" = 2718623027941064481;
    gaiVersion = "3.10";
};
timestamp = "2014-11-14 11:33:17 +0000";
}

      

        
        
        
      

    

Any idea why I am getting -1 http status?

Thanks for watching.

EDIT

Looking at this further, sometimes I get a 200 status in an app that doesn't work - I'm guessing -1 indicates a temporary network error (my internet connection was pretty unstable this week!)

But even with a 200 answer, I still don't see the data in GA.