I had my Panasonic nn945sfx for a little over a year . I thought my sharp micro was going out so I bought the Panasonic reasonable . last December the sharp died I opened up the new never opened Panasonic. I have only had use of it for six months. yesterday I set the power level set the time hit start . light comes on nothing else then oven switches off. what can I do Panasonics performance obviously isn't what it used to be please help