What do I do if a university does not inform me of my masters application status?
There are multiple questions that remain unanswered here:


Did you meet all of the deadlines for the admissions process? 
Did the people who wrote your letters of recommendation send in their references on time?
Did the school promise you a reply-by date?
If so, why did you not contact them at that time?
Did you get an email confirming that the application was complete?


If any of those were missing, then it's entirely possible that you didn't have a complete application—in which case, the school is not necessarily required to do anything, because they don't have a complete record to consider.

Moreover, a lawsuit is a horrifically bad idea under the circumstances—it's far more time-consuming and expensive than anything you're going to get back from the school. It's a waste of your time and money (unless they rather unlikely made written promises of admission, in which case they may be in bigger legal troubles than just having to return an admission fee).