I purchased a 2 gal double wall drinker to set on a heated base. My chickens have used the same style of drinker along with the cup style with no issue. When all other water sources are removed from the run they still refuse to drink from the new 2 gal drinker on the heated base. I have adjusted the height, checked that they aren't being shocked due to electrical short. Same location as the old drinker. Why would they refuse to drink from the new drinker? They are completely aware of the fact that it contains water. Have dipped beaks, lightly splashed to attract attention and tried to lure them with treats. I'm confused...