Probably public proxies which is a big no-no. They die within seconds. You probably have no live proxies. Switch to semi private proxies. If you don't, then even god cannot help you.
@yuri - I would never accept SER proxy checks as the final authority on whether they work. First of all, I typically ignore the proxy check. Why? Because I test them in 3 other software: Scrapebox, Kontent Machine, and SEOSpyglass. 90% of the time the proxies work just fine in the other 3 software, so I view it as a false negative.
Yes, I get the occasional real proxy issue, and get it replaced. Just this past week, SER proxy checker said most of my proxies were not working, and I hit 400 LPM. So you absolutely must cross check with other software to validate they are working. Like I said, typically they are working fine - so ignore the log.
Comments
I already added 30 semi private proxies to my GSA in a few previously time, but now I see their status are "Not working" and still can't fix.
What I'm gonna do?
How you increase LPM to 400
My SER always hit less than 10