expect_lpunlock: 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 Debian possible default full paths are:

/usr/bin/expect_lpunlock - from package: expect

You may install the required package with command apt-get install {package}

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