potterton suprema 50

First time useing this forum.
Boiler is not igniteing.
Red light on. If you press the reset button green light comes on for a second or two then goes off.
Pressure gauge shows 1 bar.
Has been giving problems over last few months, and by switching off power to it and back on the boiler would ignite and work normally for a period in time.
When i started looking at the problem pressure was only 1/2 bar. I pumped up the pressure tank to improve pressure, but still have problems. Can anyone help please

If it hasn't been serviced recently start there, but expect to replace the pcb at considerable cost.

Changed pcb and all seems to be working now. Thanks for the reply