As you might know from troubleshooting guide. Some proxies do not support IPv6.
However if you have IPv6 enabled, your computer might ask a proxy to connect to IPv6 version of website instead of IPv4.
Below is quick guide how to disable IPv6 on Windows 10 PC.
1. Open Start menu and search for Control Panel.
2. Enter control panel and then find Network and Sharing Center
3. Enter Network and Sharing center, in left sidebar look for Change Adapter Settings
4. Find your network card which is used to connect to internet and double click.
5. Enter properties.
Then unmark IPv6 as shown on the screenshot:
