Selgas
What has probably happened is the grease lubricating the mechanisum behind the push buttons has solidified and will not allow the main burner button to activate the slde plate behind it. You would be better advised to call a service person who is familiar with this water heater to undertake the remidial work for you – it is a little tricky and if not completed correctly can cause a very bad outcome and non of us folks want that to happen – remember a little knowledge is a very dangerous thing with gas appliances and they should only be repaired by competent qualified people.
