How to set up ipv6 on pc?

Question

proxy

I bought a proxy ipv6 for rent, entered them in the browser settings, Google works, I go to the mail to register mail, it does not open, the same story with the 2ip service, in general, proxies do not work on all sites.
How to fix the situation?
The proxy checked on the site of the seller of the service, the workers, IP login and password, popt entered the correct ones.