You have to provide a screenshot of the issue for those two sites and url examples of the problem related to those sites for anyone to verify or replicate what issue your asking specifically. Just saying can't access YouTube or FaceBook doesn't tell anyone reading much as that is so general and doesn't give detail to the problem.

Are you using a proxy or VPN?

You can check the connection settings.

• Settings -> General -> Network: Connection -> Settings

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors
• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can
• https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites