What Firewall do you use? It's possible it is blocking Firefox from accessing the internet when it updates. Try to read Configure firewalls so that Firefox can access the Internet and Firefox can't load websites but other browsers can

I never faced this problem. may be because of your antivirus.

Could be your firewall does not recognize the new Firefox version. Remove firefox.exe from your firewall allowed programs list, restart Firefox, allow it access to the internet and/or change any firewall settings to allow access.

• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating
• https://support.mozilla.org/en-US/kb/configure-firewalls-so-firefox-can-access-internet (if your firewall is not listed at the bottom of this article, either consult your firewall manual or visit the forum for your firewall and post a question there)