Old clear blue tests?

I had an a 20 pack of advanced ovulation predictor kit that I bought over a year ago. I had only used 2 tests out of it (both empty smilies)
I started using them again with same test monitor. First da I had an empty circle, bu have now had 8 flashing smilies in a row. I am on cd 23.
Could it possibly not be working because the test are old?