instructions for greenbrook 7 day immersion heater timer t23b-h

hi just moved into a rented flat it has underfloor heating which is controlled by a greenbrook timer, turned it on about last week and it worked fine, turned it off for a day and when i turned it back on again its not heating up at all even when i put it on permanently on, could possibly be the fuse as i saw a blue light flash from the fuse box, but if anyone knows anything about setting or using the timer id be grateful as i dont have a clue. I reset it yesterday
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