Tests are not working.

I recently purchased the Clearblue ovulation test. I have been using an app to help me calculate my fertile window. The test came with ten test so I started testing 2 days before my fertile window. The first day showed low symbol and the second day showed that I was at peak. That symbol never disappeared after using it the second time and now it no longer reads any strips. I am not happy. I paid a good amount of money for these tests and they are completely in accurate.