Fault 22 on EcoTecPro24 Vaillant Boiler?

This morning, I woke to find my Vaillant boiler wouldn't start up. A red light is flashing where normally a green one flashes.

On the display screen it keeps moving between F22, O.1bar and 0.2bar.

I assume that this is Fault 22 but am not sure what that means. I was hoping that bleeding the radiators might help. But having done that today, I have found no change.

Any advice would be most welcome as my landlady doesn't like spending money on us, and I am rather hoping to avoid the confrontation of having to get someone in.