I can't speak on what the issue truly is, but based on their tweets it's not as simple as expanding their cloud services to allow more but it's something with the code that needs to be updated and fixed. They obviously didn't plan for success.

@ Chris
Thank you for the clarification.

Basically the code needs to be updated I assume

So they are stating they built an MMO with the intention of having little to no players, and wrote bad code that can't handle success?