Hello.
My domain is: http://registral.by
My hosting provider, if applicable, is: Unix.
The operating system my web server runs on is (include version): OS CloudLinux
Yes, you are both right. CloudLinux is basically CentOS + kernel patches + some userland utilities and patches. It is usually fully compatible with any software that runs on CentOS.
rg305 raises a good point in that CloudLinux is very commonly paired with cPanel (and other hosting panels). If you are using a hosting panel, then you should look to use the native Let's Encrypt integration of the panel, rather than installing Certbot. Certbot doesn't understand how to configure hosting panels.
According to their features' list, you will have free Let's Encrypt certificate when you are on "Optima and Profi" plans.
If you are on those plans and are trying to renew your certificate, please contact your host and they should do it for you (automatically, by AutoSSL or something else).
If you are not on those plans, how did you get the certificate in first place?