Recently launched a new WordPress site hosted on Pantheon and I'm having issues with each of the popular webp plugins:

1. Converter for Media - Stores the webp files in outside of wp-content/upload, which is where Pantheon expects all site files to be stored.
2. EWWW Image Optimizer - This plugin supposedly stores all files in wp-content/upload, but when I run the bulk convert and then refresh the page, all the converted images disappear.
3. ShortPixel - Stores backups of the original files outside wp-content/uploads (in ShortpixelBackups/).

Hoping there is a trick to using one of these plugins or another plugin that is compatible with Pantheon.

EDIT: I'm a dummy. The EWWW Image Optimizer plugin is working, I just didn't realize that when you run the bulk optimize, that after it runs it shows you a list of images which you have to then click "Start Optimizing" to complete the process. I thought it was already done optimizing.