Potterton Promax HE not firring

[Speedshery]

Hi,
I have a Potterton Promax HE boiler. Which has not been on for central heating for the last 2-3 month.
The problem is, it works fine with heating the water in the water tank. However when I put the thermostat up for the central heating, it struggles to start.
It keeps trying to fire around 3 times then it sort of give up and the central heating is not working.

Can any body help with this problem?

 

[Agile]

It seems likely to be the kind of fault which we don't give DIY repair advice on here.

Get a professional.

Tony