This morning, I turned on my Hanna Phosphorus ULR checker all OK, pressed the button again to begin testing and nothing. Held the button down and nothing, it stayed on. Took the battery out and put it back in again, turned on, same problem. Changed the battery, same problem. Has anyone else seen this issue with this or any other Hanna checker? Cant see a reset button any where but I now have a checker that turns on then ignores all button presses thereafter!