isofilter0: 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/isofilter0 - from package: prover9

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

Error in other languages:
isofilter0: bevel nie gevind nie
isofilter0: comandă negăsită
isofilter0: comando não encontrado
isofilter0: commande introuvable
isofilter0: command not found
isofilter0: käsku ei ole
isofilter0: không tìm thấy lệnh
isofilter0: komanda nerasta
isofilter0: Kommando nicht gefunden.
isofilter0: kommandot finns inte
isofilter0: komut yok
isofilter0: nie znaleziono polecenia
isofilter0: níor aimsíodh an t-ordú
isofilter0: no se encontró la orden
isofilter0: no s'ha trobat l'ordre
isofilter0: opdracht niet gevonden
isofilter0: parancs nem található
isofilter0: perintah tidak ditemukan
isofilter0: príkaz nenájdený
isofilter0: příkaz nenalezen
isofilter0: команда не найдена
isofilter0: командата не е открита
isofilter0: 命令找不到
isofilter0: コマンドが見つかりません