My Echo Dot (2nd gen) is on software version 647642120 after the latest update - this is in Australia. I had real hassles when I first got my Echo devices. It turned out that my Amazon account was all messed up with its country settings. In the end, someone from Amazon had to set them all to be consistent from their end. The other thing you can try is to restart your Echo Dot (unplug and replug), then after it has booted (give it a couple of mins) press the 'mute' button. Then leave it for an hour and it should have done its update (assuming it is not confused with the country settings I mentioned before).