Generate WebP mark-up option doesn't work, WebP images won't show up

The Generate WebP markup option replaces <img> tag with <picture> tag.

There could be a few possible explanations why this feature doesn't work:
- the images are served via JS mechanisms.
- some CDN services restrict the use of WebP files for the free plan users. For example Cloudflare.
- a cache solution is serving old pages.
- you used a page builder for page creation. Currently this feature doesn't work well with pages created with such tools.
- when using S3 Offload plugin make sure you turn off this option "Remove Files From Server. Once a file has been copied to S3, remove it from the local server."

If none of these is true for your case, then you could try an alternative solution like Cache enabler plugin or contact us to investigate your case.