lp-check-membership: 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/lp-check-membership - from package: lptools

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

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