My Panasonic microwave oven (model NN-SD698S) had a door latch stop engaging after a few years. It turns out this is a common failure for Panasonics: the latch mechanism is screwed to an unsupported sheet metal bracket, and over many open/close cycles, fatigue prevents the bracket from providing enough lateral pressure to engage. Here is a YouTube video clearly showing the mechanism, and a quick fix (reverse bend the bracket slightly): https://youtu.be/RWVbHDMbl7Q
This fix worked for me for a couple of years, but eventually it, too, will fail. I 3D printed a small hook of appropriate size to affix to the interior cavity wall that captures the end of the mechanism and keeps it from flexing. The hardest part of this project was figuring out how to attach plastic to sheet metal. Not an exciting or difficult print, but it's kept my microwave going for years after I'd have had to junk it.
View the youtube video in the description to get an understanding of what is going wrong and where all the parts are. You do not have to unscrew the mechanism. Figure out where you are going to attach the hook. On my model, there is a flat 45 degree section at the end which is suitable. On other models, the curve of the interior cavity wall opposite may not make that possible, but there should be somewhere that works.
Test the hook
Engage the hook and hold it to your proposed mounting location with one hand, and test the door latch with the other. It should open and close securely, like new.