Sime 100c power tripped pressure ok can't re-ignite?

Hi,

Hope someone here can help. My Friends Sime Format 100c combi boiler seems to have tripped. There are no power lights and after topping up to get the pressure back up to a working level (Isuspect the low pressure caused it to trip) it still will not re-ignite using the method in the instruction book.

Is there something inside that needs switching back on?
Is there an internal fuse that may have gone?
Could it be something more serious?

Many thanks

Paul