Make sure you are not blocking content.

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(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}

Hi FredMcD, I tried starting Firefox in troubleshoot mode and the problem is still there.

cor-el said

This could be a problem with High Contrast Mode on Mac. See "New" in the release notes.

• https://www.mozilla.org/en-US/firefox/91.0/releasenotes/

Firefox now automatically enables High Contrast Mode when "Increase Contrast" is checked on MacOS in the Accessibility settings.

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Make sure you allow pages to choose their own colors.

• Settings -> General: Fonts & Colors -> Colors: "Override the colors specified by the page with my selections above"

Try "Never" if the default "Only with High Contrast themes" isn't working.

• https://support.mozilla.org/en-US/kb/disable-high-contrast-mode-firefox

cor-el said

This could be a problem with High Contrast Mode on Mac. See "New" in the release notes.

• https://www.mozilla.org/en-US/firefox/91.0/releasenotes/

Firefox now automatically enables High Contrast Mode when "Increase Contrast" is checked on MacOS in the Accessibility settings.

Ah ha, I unchecked "Increase Contrast" and that fixed it. Thanks!

Glad to help. Safe Surfing.