vncconfig: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/vncconfig - from package: tigervnc-server

You may install the required package with command yum install {package}
Error in other languages:
vncconfig: bevel nie gevind nie
vncconfig: comandă negăsită
vncconfig: comando não encontrado
vncconfig: commande introuvable
vncconfig: command not found
vncconfig: käsku ei ole
vncconfig: không tìm thấy lệnh
vncconfig: komanda nerasta
vncconfig: Kommando nicht gefunden.
vncconfig: kommandot finns inte
vncconfig: komut yok
vncconfig: nie znaleziono polecenia
vncconfig: níor aimsíodh an t-ordú
vncconfig: no se encontró la orden
vncconfig: no s'ha trobat l'ordre
vncconfig: opdracht niet gevonden
vncconfig: parancs nem található
vncconfig: perintah tidak ditemukan
vncconfig: príkaz nenájdený
vncconfig: příkaz nenalezen
vncconfig: команда не найдена
vncconfig: командата не е открита
vncconfig: 命令找不到
vncconfig: コマンドが見つかりません