Myunte 20es?

We have a Myunte 20ex heating system, before xmas when you would turn the heating on it would only come on if you turned on the water with it, and then it came on upstairs first and about 45mins later down stairs would heat up. You could turn the water off after 20 mins or so it was just to start it up. Now all of a sudden the heat does not come on upstairs and still takes 45mins for down stairs I now have no heating at all upstairs and in the hotpress there is two white box's and only one of them has a light on can any one please help me as to what might be wrong..and how we can fix it? Tks