If you reset the trip last last (no idea of excact time here) its possible due to the E7 timings it hasn't had sufficicent time to heat the water. However if you reset the trip before midnight it should be sufficient. It's possible there is a fault with the appliance that caused the tripswitch to activate and this could esplain the lack of hot water.
Try turning the switch on and see what happens. If its faulty it'll only activate the tripswitch again, if its working normally the water might heat up, as I "think" that that switch is the on/off for the heating cylinder. (i'm working from memory here as the only personal contact i've had with e7 heating is a firends flat several years ago)