And again, you get it backwards.
It's isn't "believe that god isn't real"
it's "not believe god IS real"
There is a BIG difference between the two. The way you stated it assumes that god is real and that atheists are making an effort to not believe. You are assuming your conclusion, turning the claim on its head, and trying to place the burden of proof on atheists. This is false reasoning, but sadly, quite common among theists.
The second, correct statement, places the burden of proof where it belongs - on YOU.
YOU make the claim that a god exists.
YOU have the burden to provide evidence supporting your claim.
The reason atheists don't believe in your god is simple - in the thousands of years that people have been writing down their history, for the thousands of gods who have been named, described, worshiped, and eventually forgotten, not a single shred of verifiable, testable, solid evidence has ever been provided, to support any of those gods.
Not one piece.
THAT'S why atheists don't believe you - the long history of complete and utter failure by theists. This is just one more in a long line of religious fantasies.