It is possible that your firewall or other security software blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access to install for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

• https://support.mozilla.org/kb/fix-problems-connecting-websites-after-updating

Thank You......but where is the Permissions list....datum

datum100 said

Thank You......but where is the Permissions list....datum

Hi datum, that depends on your security software, and whether it has "program control" meaning it allows/blocks individual programs from accessing the internet.

Some Windows 10 upgraders have also needed to reset the Windows TCP components. See: After upgrade to window 10, cannot access internet from firefox or chrome.