If you look at the left-side of the address bar when you are on the website you are having issues with, do you see a little image icon? It would be next to the lock icon.

If you see that, it means that Firefox is blocking the website from accessing some image data from your computer. That's often blocked because it can be used to track you, but blocking that may prevent some images from loading or displaying properly, especially on services like reCAPTCHA that depend on tracking data for verification purposes.

If you click the image icon, there will be the option to allow the website access to the necessary data. There's a checkbox that you can uncheck if you want to only allow the website temporary access to that permission, which will allow you to complete the reCAPTCHA.

Hope this helps.

Make sure you are not blocking content.

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}acking-protection-firefox-desktop