feelpp_qs_nlopt: 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/feelpp_qs_nlopt - from package: feel++-apps

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

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