A1 code on Optimax HE 38c Model?

Hi I have an Optimax HE38C Model less than 15 months old Showing A1 fault has been going off in the middle of the night for the last week (thought it was gas pressure low on main) went off this morning but won't restart water pressure above 1.2bar syphon filled and unblocked, ignitor clean no engineer available until next Monday cant get through to Ferrolli technical any suggestions?

Thanks