Defective test strips

​Hello, I recently bought the Clearblue Fertility Monitor Test Sticks, 30 ct, and I used about two and on the third try the screen showed a “test stick” on the top left of the screen. I tried it two more times and it says the same exact thing. When before it’d have a clear result. Does this mean it’s defective or did I do something wrong? Please let me know​

​Best wishes,​

​Frances​