Press control Watertech help please

I have a high powered water pump that I use to pump water from a large rain water container. It is connected via the device above. the press control has packed in. I am unable to ascertain the correct replacement. I think I have found it but the prices vary so much I suspect I am missing something. The device is labelled: Prescontrol Watertech 230v 50-60 hz, max 16(8)A Max 1MPa(10bar) Max 1.5kW Inside there is what seems to be a part/ser No 412835 06 001 230VAc Primarily it switches the pump of if there is no water flow. The problem is it never switches on. All help appreciated.
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