As you have established that your Infra Red sensor board on the TV is not working, then of course pressing the power on/ off button will have no effect.
Where did you buy your TV, were they offering a multi year warranty included in the purchase.
When did you buy your TV, was it over 12 months ago.
Sony TVs normally come with only a 12 month warranty, sometimes Sony do offer 5 year warranties
on certain models but you have to apply and register for that within 90 days of purchase.
The first point of contact for an in warranty repair is to the reseller of the TV.
