You may be working from a location that uses a firewall. This could be a place of employment, a military base or somewhere else. If you don't have access to an off-site computer, you might want to try disabling your firewall.
NOTE: If you disable your firewall, remember to turn it back on when you have completed your research. You may also need permission from an employer, supervisor or superior before disabling your firewall so please use common sense and follow the expectations of the organization when using their network.
Disable firewall settings on PC
Disable firewall settings on Mac