Your boiler's control system has lost contact with its solar hot water controller, so the solar part may not work, but your central heating and hot water from the boiler are usually still fine.

DIY fix possible

Switch the boiler off at its power isolator or fused spur, then wait about 60 seconds before switching it back on.Check that the cable linking the boiler to the solar controller (Vitosolic) is firmly plugged in at both ends, without opening any boiler casing.If the code returns after a restart, leave the boiler running and contact a Viessmann-registered heating engineer to check the solar control module and communication cable.