Fault F1:
Lack of gas or ignition problems 
Flame supervision failure 
Burner on but flame indicator off 
Minimum burner pressure too low
That is the FEB 24ED. 
The FEB 24E flashes a lamp to give fault codes.
Manuals for both are available here:
https://morcoproducts.co.uk/manuals.html
                
 Ohg
                
 February 2022