Suppose an ever-truthful dictator tells you that he is interested in the truth value of a proposition p solely about the laws of nature and how the world was like 1000 years ago. He tells you that in an hour he will infallibly find out whether p is true. If so, he will execute you. If not, he will let you go free.
Unless you have a time machine or a God who answers prayers before they are made is on your side, fatalism is surely the appropriate attitude. There is nothing you can do about whether you will be executed.
Next suppose that determinism is true. That shouldn't affect what was just said. Determinism does not create new supernatural powers to affect the past.
Now add that your identical twin is told by the dictator that he will be executed if and only if he scratches his head in an hour.
Finally suppose that your proposition p is the proposition that one thousand years ago the universe was such as to nomically determine that in an hour you will scratch your head, and suppose that the dictator's infallible method for finding out whether p is true is simply to see if you scratch your head. Then you are in the same boat as your twin! Each of you will be killed if and only if he scratches his head. Since fatalism is true for you, it's true for your twin. Thus he can't do anything about his execution, and in particular he has no freedom about scratching his head. And so compatibilism is false.