Advanced digital opk... More then one use?

Hi last month i purchased the advanced digital opk. I used only a few sticks as my fertile days were detected within a couple days. This month i tried using it again and inserted a tester stick..... Nothing happened. No blinking nothing it was a blank screen. I carefully ejected and tried again still nothing. Is there a reset button or something i can do? These tests are pretty expensive to just toss.