Set Appliance State:

Mains Power Off
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Fault code E00 is usually only shown briefly before the boiler detects
a different "E" fault.
Does the boiler show an additional fault code before or after displaying E00?
Different fault code also shown - use this fault code for diagnosis
Boiler remains on E00 fault code