You created the wrong kind of variable.
You set the wrong paragraph or character style to pick it up from.
You set the right paragraph style but it does not appear on that first page.
You applied the wrong master page.
You have a white rectangle on top of the text.
... I can think of even more, without seeing an image of that page and/or your definition and/or the master page.
I forgot the most likely cause! You applied this paragraph style to a blank line *before* the one tou actually wanted to pick up as "first".
Oh, just to tell I've already solved this problem.
It would be helpful to other usesrs who find this thread looking for answers in the future if you posted what the solution/problem was...