I’ve got the same problem.
My images are publicly accessible, and I’ve tested from an incognito window.
On loading the page for the first time, the images don’t show. They then show when I refresh the page. The same problem happens when I clear the cache (I’m using Cache Enabler, which is a simple plugin, but many including myself have found it results in faster pageload speeds than WP Rocket)
When I right-click on the broken image and open in new tab, I’m taken to a page that says:
400 Bad Request
Statically cannot download remote images, backend returned an unexpected status code (502).
And the url of the image is:
https://cdn.statically.io/img/mywebsite.com/images/imagename.jpg?quality=100
When I refresh the page and the image is showing, there’s no evidence that the images are being served by statically. They’re in .jpg format, not webp, and when I view source, the images still have their original local ftp source url’s (https://mywebsite.com/images/imagename.jpg), there’s no mention of statically around the images, only two mentions in the header of the page:
<link rel=”dns-prefetch” href=”https://cdn.statically.io/”><link rel=”preconnect” href=”https://cdn.statically.io/” crossorigin><meta name=”viewport” content=”width=device-width, initial-scale=1″>