Hello @coopero1,
The issue should not be related to the custom code. If the webP image exists, the web-server will serve it upon browser’s request. However in this case, there are two images for which webP versions do not exist. I confirmed that by just opening the image in my browser and adding .webp to the filename in the URL. Our plugin generates webP versions of the images for which a correct database records exist. In order to achieve that , the image should be uploaded via the default media upload feature of the WordPress app.
I would recommend the following steps. Regenerate WebP images and test after cleaning the cache. If the webP versions still do not exist, then, re-upload one of them using the mentioned default WordPress feature and regenerate again.
If the issue still persists after the above recommended steps, you can open a new ticket from your SiteGround User Area so we can investigate the case further.
Regards,
Dimitar