Sadly I’m at work and cannot watch the video, so sorry in advance….
Does the same gcode work from Pronterface if you run it on the PC? If so, it’s possible there is something weird with the way they ported Pronterface to the PI.
Since you can control the movement manually, the PI itself can and will run the MPCNC, your problem appears that Pronterface is not reading the gcode correctly.
EDIT: I did a bit of looking around, and have a question: Have you installed all of the necessary dependencies for python?
sudo apt-get install python-serial python-wxgtk2.8 python-tk git-core
The write-up I found is here :http://www.britishideas.com/2012/09/29/setting-up-raspberry-pi-for-3d-printing-with-reprap/
And if you continue to run into any problems there are some good comments on that thread that may help, and if not, I’m sure someone here will be able to help further.