Invalid certificate when connecting through American proxies, why?

Question

proxy

There is a "preproxy" made on 3proxy. When connecting to it, it redirects the connection through other proxies from awmproxy.com
So, everything works fine, but when connecting to proxies from the USA, the browser does not see the certificate, it shows this:

The connection is not secure

Invalid certificate

At the same time, everything works through any other countries:

Valid certificate

What could be the problem?

Answer 1

Someone is trying to intercept traffic between you and the proxy (for example, the provider due to blocking the ILV) or between the proxy and the site. And what is shown if you temporarily accept the certificate (after clearing the cookies)?