service vsftpd start
Though "restart" works too.
Should work if your're using systemV
If you're using systemD
to list all services registered
systemctl list-units --type service --all
assuming vsftpd is listed you need to check it it's enabled.
systemctl is-enabled vsftpd.service
assuming it's there and registered, to start it.
systemctl start vsftpd.service
Then check the status
systemctl status vsftpd.service
hope that helps.