I think the water did it. You should probably not put any water in it. I made mine a few days ago. I used 1 lemon, half a kilo of sugar and a spoon of salt. After it boiled it became very dark brown, and also pretty hard.
Get a good piece and warm it up in the microwave for 3 seconds or so. Not more than 5 seconds or it won't work.
The problem I had was that while I was working with it, the paste just kept melting in my hands which kept becoming warm. Keep making it a 'ball'.
Hope this helps.