I have this funny issue where a webp video is not always showing in the viewer pane. In fact, it only seems to be recognised directly after viewing a webp image first.
Please check this video in which I try to preview the webp video after first viewing a JPG file, and then after viewing a webp image:
Try disabling the WebP plugin, as it doesn't do animated WebP. Not sure why it's only falling through to Edge some of the time and not others, but that may fix it.