I'm unable to open webp files in Photoshop Elements v. 13.1. I see that (in a Program Files folder for Adobe, Elements 13 Organizer, Plug-Ins, File Formats)
WebPShop is a Photoshop module for opening and saving WebP images, including animations. Important note: Photoshop 23.2 and newer natively supports WebP.
Copy the plug-in file inside the plug-in directory you can find in C:/Program Files/Adobe/Photoshop CC/Plug-ins, restart Photoshop and you should be able to ...