Ovulation test fail

Hello. I have been using your ovulation tests and the last two tests that I have tried to use appear to have not worked. The first two I used were fine, a line appeared for the results. The last two, nothing. Each individual test has CP0545/9 2015-09 254 11:00 on it. I did not save my receipt as I did not expect your tests to fail. What should I do now?