Hello my name isXXXXX will be assisting you with this problem today. Thanks for trusting us to help you with this appliance
The H98 error means the problem is either going to be the magnetron, inverter or control board. This is not a good DIY fix because factory test equipment will be needed to accurately diagnose the problem plus the unit stores lethal voltage even when unplugged.
I recommend you take the unit down and take it to a experienced workshop to have it fixed. The cost would be anywhere between $150 - $250, Bearing in mind that most new units cost around $229 you may want to look for a new unit.
After the warning given if you decide you want to fix this yourself and have a multi-meter and amp meter I would be happy to assist you further :)
I would like to earn your highest rating, are you totally satisfied with my answer? If not please reply to me with your concerns or additional questions. If I have answered your questions to your satisfaction, please don't forget to rate me before you leave.
It was my pleasure helping you today. Feel free to get back to me here at any time if you have additional questions at no further charge. Sometimes I will have to give bad news, Please try to find it in yourself to rate me for the service not the bad news.
Please also remember if you have future questions regarding a faulty appliance, You can request me personally to assist you with the problem :)