Update about the issue. (In case someone else encounters the same problem.)
I wrote to Siteground support. They fixed the issue for me by creating a symlink on the server.
So the plugin needs additional server settings for WebP option to work with subsites of multisite .
But for the primary site of multisite it works without any problem or additional settings.
Hello!
I have the same problem. Enabled WebP images option, conversion completed successfully, I see WebP images in filemanager. But site still serves only JPG and PNG images.
I tried to clear cache, used different browsers in incognito/private mode. But the problem still exists.
It is a multisite of my client, it is hosted on Siteground. And I enabled WebP option only for a subsite now.
Here are a few links to subsite pages:
https://www.luxlvl.com/luxlens/architectural/
https://www.luxlvl.com/luxlens/commercial-spaces/
The homepage of subsite (https://www.luxlvl.com/luxlens/) redirects to home page of the primary site (https://www.luxlvl.com/) so please don’t use it.
