Simple paypal shopping cart variation options don't show

I have used the following code to create a product variation. However, when you click Add to Cart, no options are shown – just the new product name and price.

I can only find one thread dealing with this and the solution was not applicable to this example.

[wp_cart_button name=”The Bird of Time e-book” price=”9.95″ var1=format|epub|mobi”]