I try to build Slicer on my mac, but error happens, I try both http and https, and try open and close firewall, but cannot solve this problem.
In China, If you use a proxy server, make sure CMake is able to use the proxy properly. You may need to set the proxy information in the CMake configuration option or adjust your network environment based on the proxy Settings.
Here is an example,
export https_proxy=http://127.0.0.1:33210 http_proxy=http://127.0.0.1:33210 all_proxy=socks5://127.0.0.1:33210