Same thing happened to mine so I called Ideal and they are sending me a new cable for free.

Something else I've found is when the receptacle shows no ground I remove the cable from the suretest front and plug it back in. Personally I don't like the idea of having to fiddle with my testing equipment to get it work right. I've had to send my unit back once already and am thinking of just putting it aside and looking for another circuit analyzer.

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Principles don't change with circumstances. That's what makes them principles.
-George Colombo