Truma Ultrastore - No gas water heating

Spanielzrus

Folks,

Had a search on the discussions but cant find an answer.

2010 Sterling Europa 565 fitted with a Truma Ultrastore Gas/Electric water heater.  Works fine on Electric. When I try to fire up the gas heating, the control panel green light comes on, the solenoid 'clicks' and the ingnition can be heard trying to light
the gas without success.  Red light comes on after about 10 seconds.

1.  Gas is getting through.

2.  The battery is well charged.

3.  The vent cover is off and the vent does not appear to be blocked.

Any suggestions would be gratefully received.