ppl_lpsol: 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/ppl_lpsol - from package: ppl-utils

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

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