Get File Access to save game state

When I try to create a file, the task never completes:

var task = Task.Factory.StartNew(async () =>
    Windows.Storage.StorageFolder storageFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
    stream = await storageFolder.OpenStreamForWriteAsync("save.sav", Windows.Storage.CreationCollisionOption.ReplaceExisting); //await never returns

I guess that is because I don’t have the proper file access.
-I tried looking at the appxmanifest but can’t find any capabilities that match with saving files.
-I tried adding the file type to appxmanifest Declarations.

This may help: