As stated on the headline banner that is posted on the Frontier Support page:
"Although the recent Xbox Live outage looks to be largely resolved, it seems that some services may still be affected. This is impacting our ability to sync Arx balances and cosmetic purchases for some Xbox users, though other functionality may also be affected in rare cases. We're watching this closely and expect it to be resolved soon."
Therefore, obviously, if you ask Xbox support, they will say that they have resolved their issue regarding Xbox Core Services (Xbox Live), and if you ask Frontier Support, they will say that the current connectivity and Arx problem lies with Xbox.
Which, of course, leads to the conclusion that no actual answer as to why this is happening to the Xbox ED playerbase will be given by either support teams, at least for the time being.
We are stuck in the middle of a technical abyss.
Although it may be hard to do for some, the best remedy for the current Xbox ED situation is just to temporarily walk away from the situation (in other words, stop playing the game). When the issue (regardless who is at fault) will be rectified is unknown, and trying to connect to Frontier servers through some "MacGyver" method is simply pointless (even if you do connect to Frontier servers, you usually get disconnected soon afterwards, or are unable to connect with friends or squadron, and do not earn any gameplay Arx).
At this point, after dozens upon dozens of "bug reports" have been submitted regarding no connectivity, no Arx, no livery, no store, and in some cases, no Horizon or history of even playing the game, all the Xbox ED playerbase should do now is check the forums, or the Frontier Issue Tracker, once or twice a day to see if there is an announcement that services have been returned to normal.
On a side note, I somewhat believe that this situation will fix before the release of the over-hyped Fleet Carriers (which is suppose to be happen around June, and which will bring a whole new set of game-breaking issues). It definitely would be an enjoyable sh*t show to watch if Fleet Carriers were to be release and Xbox players were still dealing with these important game-breaking issues.
Fun times for sure.