Hello!
There are a few potential culprits in terms of plugin conflicts that may be contributing to your problem.
WebP Express appears to try to route requests for images to a WebP extension. This may be interfering with the way that our plugin may be trying to rewrite requests to go through the CDN.
Better AMP may be doing similar things in terms of interfering with the way that Shift8 CDN will rewrite requests for static assets.
To rule these out, try disabling WebP express first, and see if the issue resolves. If not , try disabling Better AMP and see if that resolves your issue.
If these steps still dont resolve the issue, feel free to let me know your site url so I can attempt to analyze the site. If you dont want to share the url here, feel free to email [email protected]