Overload switch
If the wall socket has power, check to see if there's an overload switch on the hot water dispenser housing. If there is, reset the switch (usually by pressing it in), wait 15 minutes, then try the tap and see if the water coming out is hot. If there's no overload switch, there may be an internal fuse on the unit. To see that, you need to remove screws and a panel.
Heating element
If there's no overload switch--or if the unit still doesn't heat--the heating element may be burned out. If so, it may be replaceable. We would need your Model number to find the correct parts.