Firefox cannot load pages that other browsers can, but the 'help' page for this issue did not fix the problem.

Question

I am troubleshooting an issue occurring on a family member's pc. Immediately after changing their "search" settings from "Yahoo search" to "Google search", they found that Firefox was unable to load any webpages. After troubleshooting the problem, I found the "Firefox can't load websites but other browsers can" help page, and attempted each of the solutions listed. None of those solutions fixed the issue. Also, I uninstalled and re-installed Firefox; the issue persists. However, the 'new' version of Firefox remembered the tabs left open when the 'old' version was deleted, so some temporary files likely persisted.
Are there any other steps that can be taken, or is Firefox on this computer no longer an option?

Answer 1

Start with this;
Type '''about:preferences#advanced'''<Enter> in the address bar.
Under '''Advanced,''' Select '''Network.'''
Look for '''Configure How Firefox Connects''' and press the '''Settings''' button.
Check the settings.
Some problems occurs when your Internet security program was set
to trust the previous version of Firefox, but no longer recognizes your
updated version as trusted. Now how to fix the problem: To allow
Firefox to connect to the Internet again;
* Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
* Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see
'''[https://support.mozilla.org/en-US/kb/configure-firewalls-so-firefox-can-access-internet Configure firewalls so that Firefox can access the Internet.]''' {web link}
If there is still a problem, go to that computer and do this;
Type '''about:support''' in the address bar and press '''Enter.'''
Under the main banner, press the button; '''Copy Text To Clipboard.'''.
Then in the reply box at the bottom of this page,
do a right click in the box and select '''Paste.'''
This will show us your system details.
'''No Personal Information Is Collected.'''