The Yandex crawler is blocked from accessing our servers. Their crawlers are really aggressive and generated high server load, while being responsible for only a very small fraction of legitimate traffic.
So to preserve server performance, we have decided to not allow Yandex on our servers.
As in the Let’s Encrypt Certbot? Using Certbot is great on your own server, but basically unusable for web hosting, because Certbot assumes that it has unrestricted access to the server configuration.
If you want a free SSL certificate, we provide our own tools to do so that are designed to work well with our hosting.