The Nexus v1 (the current nexus that you play daily) does not support mojang's change to allow players to change their names. In the previous news post, I mentioned that we INTEND TO and we SUPPORT this change in Nexus v2, however, you'll notice with the current game version, you can't join the server.
Minecraft versions 1.7.6 and up have added nothing to the game for the user end, they've simply changed and began to migrate functionality over to the new way of name changing. Because of this, we will NOT be supporting these new versions on the current version of The Nexus. If you'd like to be able to play, (like 1,500 players already are) you'll need to be running a version between 1.6.4 and 1.7.5.
HELP! I DON'T KNOW HOW TO DOWNGRADE! :(
I have a guide for you... and it's less than 3 minutes! Enjoy!