In Xamarin.IOS I found that Azure mobile app in offline mode wouldnt get past this line when offline.
await MobileService.SyncContext.InitializeAsync(store, new MobileServiceSyncHandler())
And if you remove the await and put a Wait at the end that just causes deadlock.
Only solution I found that works is:
System.Threading.Tasks.Task.Run(() => MobileService.SyncContext.InitializeAsync(store, new MobileServiceSyncHandler())).Wait();
This is as per Quickstarts sample so clearly they need to update it.