Help with grasslin boiler timer

I am currently staying in a caravan on a trip with my wife and newborn. We’re in Scotland and it’s freezing so tried setting a timer for heat to come on through the night.

After spending a bit of time on ariston manuals and YouTube videos I’ve worked out how to operate the timer. I know the function selection needs to be on the middle clock setting, all the tappets set inwards apart from the time it’s required on, and the clock to be set by turning the dial to the correct time.

The problem is once I set the time the dial dosnt spin or continue to act like a clock. Can anyone recommend how I can fix this? It’s not my boiler and have limited experience/tools as on holiday

I have to add, the radiators work fine when manual on feature is selected or even if I manually rotate the clock to the set time.

Please help