Turns off after 15 seconds..shows H98 on the window and wouldn't start.

H98 means the component that produces the microwaves is fried. It costs more to have it replaced than to buy a new microwave, so if it isn't under warranty, throw it away and start shopping.
May 20, 2019

My microwave shows a code H98 why is that? - Q&A - Best Buy

..WARNING on self repairs

https://www.fixya.com/support/r29874712-repairing_microwave_ovens

Easy to fix. Unplug it, wait 15-30 seconds, plug it.

https://youtu.be/hcKuRIT7pUE

If you wish to get some details; check the site linked here. Pull up older posts.
http://electro-medical.blogspot.com/

thi code refers a broken switch intelock security take it to service

control circuit problem

H97, H98 or H99 mean that there's a problem with your inverter, magnetron, or digital programming circuit.

R

H95, H97, H98 or H99 mean that there's a problem with your inverter, magnetron, or digital programming circuit.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here. If you're not in the US, see Panasonic.net.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

H97, H98 and H99 appears in display window a short time alter start key is pressed and no microwave oscillation.

NOTE:

DO NOT try to REPAIR this Inverter Power Supply (U) and also DO NOT RE-ADJUST PRESET VOLUME on the board. It is very dangerous to repair or adjust without sufficient test equipment because this circuit handles very high voltage and very large current. Off alignment or inverter board operation is dangerous. Operating a misaligned inverter circuit is dangerous due to the very high voltage and current that is produced by this board. Defective boards must be replaced with a new one.

This oven is programmed with a self diagnostics failure code system which will help for troubleshooting, H97, H98 and H99 are the provided failure magnetron and inverter circuit problem areas. This section explains failure codes of H97, H98 and H99. H97, H98 and H99 appears in display window a short time after start key is pressed and there is no microwave oscillation.
There is not a lot the layman can do except maybe to try a new magnetron.
It is a job for an experienced Panasonic Microwave repair man.

H95, H97, H98 or H99 mean that there's a problem with your inverter, magnetron, or digital programming circuit.

It may be a loose connection in the wiring between the inverter, magnetron, and/or control board, or maybe one of those components has failed.

Due to the lethal voltages used and produced in inverters, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here.

In Canada, you can find an authorized Panasonic servicer here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.