A similar thing happened to me a couple years ago. I have had my account for quite a few years and my sister made an account, using the same computer. We were both fine for a while, but one day I went to log on and it said I was frozen. I'm not sure if they gave me a reason when I tried to log in, or if I emailed to ask why. It was the multiple main account reason, whatever the case. I sent them an email explaining the situation, and got no response. I just gave up on Neopets for a few months. When I eventually went back, my account was back as if nothing had ever happened to it. Although I was kind of annoyed that I was never informed my account was unfrozen, or perhaps given an apology for the misunderstanding, I was happy to have it back.
What I mean to by this anecdote is, don't give up because there's still hope.