Ideal c24

Question

when switching on the boiler it ignites for 8 to 10 seconds, then it cuts off and the lock out lamp comes on. pressing the reset button or turning on the hot water tap has the same effect.Any ideas?The pilot does not light when turning on hot water. we leave the hot water on the go unplug and replug the electrical cord and it will work just long enough to get wet and soaped up then no hot water again. any suggestions. would like to fix it myself if possible. please advice Rheem Pronto RTG-74PVN-1