ps2sp: 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/ps2sp - from package: qucs

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

Error in other languages:
ps2sp: bevel nie gevind nie
ps2sp: comandă negăsită
ps2sp: comando não encontrado
ps2sp: commande introuvable
ps2sp: command not found
ps2sp: käsku ei ole
ps2sp: không tìm thấy lệnh
ps2sp: komanda nerasta
ps2sp: Kommando nicht gefunden.
ps2sp: kommandot finns inte
ps2sp: komut yok
ps2sp: nie znaleziono polecenia
ps2sp: níor aimsíodh an t-ordú
ps2sp: no se encontró la orden
ps2sp: no s'ha trobat l'ordre
ps2sp: opdracht niet gevonden
ps2sp: parancs nem található
ps2sp: perintah tidak ditemukan
ps2sp: príkaz nenájdený
ps2sp: příkaz nenalezen
ps2sp: команда не найдена
ps2sp: командата не е открита
ps2sp: 命令找不到
ps2sp: コマンドが見つかりません