The site is not available in 3 Russian cities. What to do?

Try to collect as much information as possible about the unavailability and to contact the technical support of a hoster.

What to do with it?

For starters figure out the reason - it could be anything from locking a resource, to curve macrotidal among providers.
Then take measures to communicate with the tech support, change addresses, change hosting etc.

Wait until you calm down LV.

If the site is available from the same town and unavailable from another - it is a question either to the city (a regional ISP can block), or to check service availability.
Try to find a few people of these cities and ask them to verify multiple proxies.

If the site is inaccessible due to locks, then to quickly make it available, you can rent a cheap vps, and put nginx on nginx proxy_pass to configure the domain name and then change the DNS a-record to the IP address of the rented VPS server.
And then you can in a relaxed pace to think, what to do and how to live (change the ip to move)

My client is so on a Hetzner IP address is in the subnet are blocked RCN. Have configured proxy_pass to him, and after a while Hetzner issued a IP from different subnet