Why do some sites not work through a proxy?

Question

C++ / C#

I already buy different proxies on which site, go to Google, check for a robot right away, passed it, then I try to google and out of 20 sites a maximum of 2-3 opens, the rest have an ERR_TUNNEL_CONNECTION_FAILED error Did
I set everything up crookedly or am I unlucky with a proxy?

Answer 1

it's not the sites that don't work, it's the proxies that suck