Go to Start > Control Panel > Network and Internet > Internet Options and disable all the restrictions from the Connections tab. Also, make sure that you don't have any Parental Controls, Family Safety, or some other similar software enabled. If it doesn't work, try to connect using a different browser and clear all cache, cookies and temporary files. Another solution is to restart your modem or router. If you still can't connect, press Windows + R key combination, type cmd and click OK. Type ipconfig /flushdns, press Enter and close Command Prompt after the process is completed. Check the Microsoft Support page for further solutions.