Stopped working after 4 months!

This product worked great at first - so easy to use! My husband and I went on the Keto diet for about 2 months; during that time it was perfect. We went off and recently started back up again. I'm 3 days in and was curious to see if my body was getting near ketosis; all strips turned grey at the bottom and do not work anymore. Working on figuring out how to have these replaced. Box says they don't expire til 2021.

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