Perhaps you have to restart the browser.

Thanks, I gave that a go but no luck.

Hi, try this: Click the 3 dots at the top right of the thumbnail again, then Edit (but don't change anything), then Save again. That has worked for me many times after getting a blank thumbnail. However there is unfortunately the occasional site that just refuses to work. The only option then is to try using the URL from a different part of the same site for the image.

Hey Scribe, thanks for the advice, tried your method out but unfortunately to no avail. Even input a bunch of different image URL - same story, preview looks nice but empty thumbnail after that.

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or userChrome.css is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Try the Firefox version from the official Mozilla server if you currently use a version from the repositories of your Linux distribution.