Paid proxies do not work at all

Hi everyone!
I have a problem with GSA SER. I bought proxies from 3 different services (1 of them has an API in GSA) and these proxies do not work.
Why do I think they do not work? I tested them in GSA SER (with test tool) with Google Search. And they displayed as “not working”. But if I test them in “Bing” or “Proxyjudge” they work! And that`s a big problem. So I tried everything and need your help, guys.
Anyway, I was looking for free proxies through GSA SER, and sometimes after testing ~150000 free proxies, it can find 5-10 working in Google Search. So that`s not a FireWall or Port issue.