I am using a MacBook Air. I get all the way to the review screen to pay with a credit card and I cannot access the pay button because it is below my window. When I try to scroll down it will not stay it just jumps back so that the pay button is below my window.
The support professional helped me out. She had me right click on the grey bar next to the file name (top of the program window) and select Icon only. While the button was still below the window I was able to move my curser down to the relative location and click the button to process the order.