Your boiler is simply reminding you that it is time for its annual safety service, as set by the installer, rather than indicating a mechanical breakdown.

Technical description

A time has been set in the Service interval function i.e. 1 to 72 months and that time has expired. Service reminder time in the Boiler settings menu (section6.5.13, page43) allows this feature to be set (1 to 72), a 0 will disable this function.