crlupdate: 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/crlupdate - from package: mono-devel

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

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