The problem asks you to print exactly: Hello, World! Notice the details: capital H, capital W, comma after Hello, space before World, exclamation mark at the end. Miss any of these and your submission fails.
This might seem picky, but it teaches an important lesson. When problems specify output format, they mean it. Computers compare strings exactly. "Hello World" is not the same as "Hello, World!" to a computer. Your task is clear: one print statement, exact string.