It's listed under MMO games, though I seem to recall having played it single player. Either way, those multi-player servers seem to go/be down a lot, it gets commonly asked about here. I guess try again later.
Wait... looking a little more closely, in Firefox, and using NoScript, I noticed I was blocking JavaScript for deadzonegame.com and playerio.com (and then some. Of course for starters, you need to allow it for armorgames.com, of course ). Allowing those two, the game loads alright. (And no, so I reckon I haven't played it before.)
I suspect in Internet Explorer, where I at least don't use such tools and am not readily aware of them, you'll often find that such stuff will work by default, simply since it isn't getting blocked; *or* and far from out of the question, it will get blocked because of whatever settings that are default or that you've tinkered with way back when, and so are very hard to think of and therefore adjust.
And so if this provides a solution in this case, I guess it may be the answer to many such questions. If it hadn't been thought of before, I don't exactly closely follow the forums here.