Stops after 2 months

I bought 3 of these. 2 didn't work. I was able to return only one of them via Amazon and a working one was sent out, but of the 3, 1 didn't work. Also, it only works for 2 or 3 months, then stops unless you pay a subscription fee, and worst of all, the readings on both of them stopped being accurate about 2 months in. So it is good for about 2 months, 1/3rd of the time.

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