Is it possible that you are only specifying for one page to be printed in the print dialog? There's several different settings that can do that.
Thanks Phil...that was it. Now can you give me a hint as to why I am only getting 9 rows of labels? The Avery form I selected has 10 rows.
That is a common issue with FileMaker and avery format labels. Your printer, like most, cannot print edge to edge. There's a maximum "printable area" a little bit smaller than 10 rows of labels plus a header and (possibly) a footer on your layout. This causes FileMaker to determine that the 10th row of labels won't fit and prints them as the first row of the next page.
But that added space that isn't fitting is likely empty white space on your layout. If you can adjust the height of the body of your layout to make it just 1 or a few pixels shorter, everything should fit in most cases. You can enter layout mode, select the body layout part by clicking it and then use the height box in the Inspector to make the body layout part smaller.