Manage > Categories.php Not Available

For whatever reason, the categories page I once had on my website: MVRed.com is no longer available. I run a few other WordPress blogs and it’s available.

I go to ADMIN – MANAGE but Categories is missing. I can still select the three I created the first day I made the website, but I can’t create any new ones.

In my database, all my posts are under id:0. I am completely lost. I am trying to put a magazine forum on my site and I can’t because I don’t have the code id’s or categories page to use it.

Can someone help me please!