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

One user had the same issue. Changing the pages zoom helped.

Check your zoom controls.

<Control> (Mac=<Command>) + (plus) enlarge - (minus) reduce 0 (zero) restore

This can happen if you use "Zoom Text Only". Best is always to use full page zoom.

• Zoom -> [] Zoom Text only

You may have accidentally zoomed webpage(s). Reset the page zoom on pages that cause problems.

• View -> Zoom -> Reset (Ctrl+0/Command+0 (zero))

• https://support.mozilla.org/en-US/kb/font-size-and-zoom-increase-size-of-web-pages

If you have made changes to Advanced font-size settings like increasing the minimum/default font-size then try the Default font-size setting "16" and the Minimum font-size setting "none" in case the current setting is causing the problem.

• Options/Preferences -> General: Fonts & Colors -> Advanced -> Minimum Font Size (none)

Make sure you allow pages to choose their own fonts.

• Options/Preferences -> General: Fonts & Colors -> Advanced
  [X] "Allow pages to choose their own fonts, instead of my selections above"

It is better not to increase the minimum font-size, but to use the builtin Firefox Zoom feature.

• Options/Preferences -> General -> Language and Appearance -> Zoom

Increase the % size of web pages - WORKS