How do I resolve the error "Communication failed" when running grbgetkey?

While running grbgetkey to retrieve a license file, you might receive the error:

Communication failed, check your network connection
or set variable HTTPS_PROXY if you need a proxy

If your computer is connected to the internet but requires a proxy, you can specify a username and password in the environment variables HTTPS_PROXY and HTTP_PROXY by setting them to http://username:password@proxy-server:port.

Commercial license users

If your computer isn't connected to the Internet or if your network security system does not allow the command below to function, we also offer a manual license key process. See How do I generate a license file for a computer without internet access? for more information.

Individual Named-User Academic license users

Please check the following conditions for the computer where you want to install the free academic license:

• The computer can communicate with the Gurobi User Portal.
• The computer is not using a proxy server.
• The grbgetkey program is not blocked by a personal firewall or an internet security program.

Further information

• How do I generate a license file for a computer without internet access?
• Where do I place the Gurobi license file (gurobi.lic)?
• What can I do to resolve an "ERROR 405" from grbgetkey?
• What can I do to resolve an "ERROR 303" from grbgetkey?