Replaced your console? MP4 support needs a license update

In short, MP4 support is licensed to the 360 console you have when the support is downloaded, not to your LIVE ID or to the hard disk. Simply redownloading the codec support is not enough. The above thread has a link (Option 1) to the page where you reassign all your licenses to the currently logged-in 360 console ID, then you can redownload them and have stuff like MP4 work when you are offline. You do need a account linked to the Xbox LIVE account to do all this.

My past experience with H264 requiring a LIVE connection is probably related to my first console failure happening before that update. Once I followed the directions, MP4 plays again without a LIVE connection.

Just in case someone else needs the directions…

Edit: original link to forum post invalid. works for the moment, until they revamp the site again…

Update the firmware

Same console and I still cannot get mp4 to play