probably when the fuel level rises above the maximum, the float has been forced up and locked. It may be that it unlocks itself, as the level of gasoline drops as MangelHH told you but if it does not and you have an electric pump, then you will have to remove it and unlock it manually by moving the float carefully and miseing if the needle on the board rises and down, which he does slowly. It is doubtful that the resistance of the meter on which the contact needle moves is damaged, when the tank is at least the needle marks high resistance and on the board the low needle and if it is full marks low resistance and the needle of the board is above marking ful, if that is damaged you will have to change the entire float except the battery that can be passed from one to another. I hope my explanation helps you and you can solve the problem