powwow-muc: command not found

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/powwow-muc - from package: powwow

You may install the required package with command yum install {package}

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