What does fault code FA flashing on a Logic Combi 35 mean?

This means there is an issue with the flow and return pipes are reversed. Although this is usually not the case on a combi boiler, If this occurs please check all isolation valves underneath the boiler are in the open position, all radiator valves are turned on full and the bypass is free flowing to see if this rectifies the issue, If it does it may be worth calling the installer of the boiler to take a look.