"Backup failed : FTP server hostname cannot be resolved" remote ftp backup stopped working...

I have a remote ftp backup configured, and virtualmin fails for some reason.

When I check in bash command the ftp connect parameters everything works fine! Any tips please?

PS A server reboot fixed the issue.
The server was hacked two weeks ago, and a cryptominter was installed. I forgot to reboot after cleaning it up (deleted some stuff in etc tmp)