Sorry boxtops, if you lift the ballcock up it stops the water flowing so it needs pushing all the way down to get the water flowing, if this doesn't work it may be frozen or the filter could be blocked as some of the new cisterns have a filter in them. To fix the latter, turn off the water and loosen the nut which attaches to the bottom of the cistern, if there is a filter you will need to lift it out, clean it, and put it back, then refit the nut to the cistern. Hope this works for you. I meant to ask, has the cistern ever worked properly or has it always been the same?