Hmm let me give you some insights
I have a fresh WP instal running on appfog.com . I have only two plugins installed ( MU domain mapping and yours). I had no problems with authorisation whatsoever. When I did backup file went to GDrive nicely, but file name was without an extension and I couldn’t preview it. After downloading it and adding extension manually it was ok, no errors during decompression nothing missing.
But I thought It would be nice to be able to see what’s in backup without downloading it. So I started to play with source. As soon as I added hardcoded mime type I was able to preview backup online but it was still missing extension. So I’ve added hardcoded extension and it started to work as expected.
Hope this will help others who might have same problem
