Go through these articles for possible solutions:

Configure firewalls so that Firefox can access the Internet (you may need to remove Firefox from the list of allowed applications, then add it back)

Websites don't load - troubleshoot and fix error messages

Server Not Found - Troubleshoot connection problems

I have removed and added firefox in firewall exceptions, no change I have turned off firewall, still no change I have reinstalled firefox , no change I have installed chrome and opera , same outcome All other computers using this connection are normal problem is isolated to this particular laptop

thank you for your reply

What Firewall are you using?

WINDOWS FIREWALL

THANKS

WINDOWS FIREWALL

THANKS