Attention: Make sure to carefully check that your credentials and port number are correct for your auth type.
HTTP
How to authenticate using HTTP.
curl --proxy http://isp.joinmassive.com:8000 -U '{PROXY_USERNAME}:{API_KEY}' https://cloudflare.com/cdn-cgi/trace
HTTPS
How to authenticate using HTTPS.
curl --proxy https://isp.joinmassive.com:4080 -U '{PROXY_USERNAME}:{API_KEY}' https://cloudflare.com/cdn-cgi/trace
SOCKS5
How to authenticate using SOCKS5.
curl -x socks5h://isp.joinmassive.com:8000 -U '{PROXY_USERNAME}:{API_KEY}' https://www.cloudflare.com/cdn-cgi/trace