How do I get my Vokers Linea 24 to fill and/or ignite?

I have a Vokers Linea 24 Boiler - I have just emptied the system, put in sludge remover and repressured the system. I am now going to let it run for a couple of weeks and then flush out.
However, the boiler is failing to ignite and sounds as if is having a problem filling.
Any ideas?