Heating programmer continuously flashing and clicking?

Went on holiday for almost a week and decided to switch timer off. When returned and switched it back on just kept flashing and engaging the boiler for a time but then cut out. Decided to get a new controller but that just kept clicking and flashing but not engaging the boiler at all. Same thing happened a couple of years ago after a holiday shut down but subsequently decided to keep the system on a very low setting. Should have done it this time I guess!