It could also mean that you missed your surge. If it was a short surge and you only test one time a day, it can be missed occasionally. Are your cycles very regular? Do you usually o around the same time each cycle?
Could mean that you haven't ovulated yet! Keep testing and make sure it is the same time every day. Also, usually noon is the best time to test...after 4 or so hours without using the restroom.
Good Luck!