Btw, why he should use mirror site? Afaik it wont change anything once the IP is used by other then he will get the same message although he use mirror sites/links.
This is true. Mirror links are usually used only to access sites which are banned by the government, but not restricted by the site itself thanks to which they are a better alternative to VPN usage in my opinion.
They don't automatically generate new IP addresses or anything due to which he would need to directly talk to their customer support for a proper resolution.