it hapeend that sudddenly i was unable to access the server via one IP (proxy), then also via my home IP, also via SSH, no access so i had to use IPMI kvm to access.
Then i tried to restart firewall or empty it and it disconnected OpenVZ VMs so server needed to be restarted.

These commands may fix the issue when IP is banned:
sudo iptables -F
sudo iptables -X
-F, --flush [chain]
Flush the selected chain (all the chains in the table if none is given). This is equivalent to deleting all the rules one by one.

-X, --delete-chain [chain]Delete the optional user-defined chain specified. ... If no argument is given, it will attempt to delete every non-builtin chain in the table.