Had the same Problem, found the fix
Hi, I had the same issue with the unit not completing a cycle and receiving the dreaded frown face. The problem is the conductivity of the water was too low for the probes to recognize they are indeed in water. Perfectly distilled water does not conduct electricity, small (microscopic)dissolved particles within the water do. In essence the water was almost too clean for the unit to work, that being said I still wouldn't risk not treating the water. I just added a very small amount of juice crystals to the water in question and the unit worked without a hitch. I also tried collecting water where wave action on the lake at the shoreline would stir enough particles in the water to make the unit work, this also worked well. Please note this is only for rare instances where water is so clean that the unit won't otherwise work. For the most part you should still try to find the clearest water possible. We must both hike in the best places to have such great water. Hope this helps.