Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

Do you see little boxes with a hex code instead of the image?

Special icons are usually supplied by an icon font that is downloaded from the server via @font-face CSS rules.

You can check gfx.downloadable_fonts.enabled on the about:config page and make sure it is set to true (if necessary double-click the line to toggle its value to true). Also 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"

If you use uBlock Origin then check "block remote fonts".

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (uBlock Origin, Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows the shield icon at the left end of the location/address bar in case Content Blocking is blocking content.

• click the shield icon for more details and possibly disable the protection

You can check the Web Console about what content is blocked

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/tracking-protection
• https://support.mozilla.org/en-US/kb/content-blocking

I have removed all extensions, add-ons and plugins but still nothing. Attaching screenshots.

This looks like an issue with a corrupted font.

What font is Firefox trying to use?

You can right-click and select "Inspect Element" to open the builtin Inspector with this element selected.

• https://developer.mozilla.org/en-US/Tools/Page_Inspector

You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Font tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website.

• https://developer.mozilla.org/en-US/Tools/Page_Inspector/How_to/View_fonts

Attached a screenshot of the inspector.

I was able to fix the issue with the solution from the below link.

https://support.mozilla.org/gl/questions/1219642