fp-2.6.4: 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/fp-2.6.4 - from package: fp-ide-2.6.4

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

Error in other languages:
fp-2.6.4: bevel nie gevind nie
fp-2.6.4: comandă negăsită
fp-2.6.4: comando não encontrado
fp-2.6.4: commande introuvable
fp-2.6.4: command not found
fp-2.6.4: käsku ei ole
fp-2.6.4: không tìm thấy lệnh
fp-2.6.4: komanda nerasta
fp-2.6.4: Kommando nicht gefunden.
fp-2.6.4: kommandot finns inte
fp-2.6.4: komut yok
fp-2.6.4: nie znaleziono polecenia
fp-2.6.4: níor aimsíodh an t-ordú
fp-2.6.4: no se encontró la orden
fp-2.6.4: no s'ha trobat l'ordre
fp-2.6.4: opdracht niet gevonden
fp-2.6.4: parancs nem található
fp-2.6.4: perintah tidak ditemukan
fp-2.6.4: príkaz nenájdený
fp-2.6.4: příkaz nenalezen
fp-2.6.4: команда не найдена
fp-2.6.4: командата не е открита
fp-2.6.4: 命令找不到
fp-2.6.4: コマンドが見つかりません