Bad serial number :(

Recently my cd key got banned and I decided to buy another key. So I use darky to change the key and open dayz commander. When I clicked on a server it opened up the loader saying please wait then went black. It brought me back to my desktop with a little box saying bad serial number given in setup. I've tried everything that I've seen on youtube and I really need help with this

Try making a new Windows account, and playing DayZ through that account.

I don't know why it works but that's what I got told to do and it worked