qhelpgenerator: 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 CentOS possible default full paths are:

/usr/lib64/qt5/bin/qhelpgenerator - from package: qt5-qhelpgenerator
/usr/bin/qhelpgenerator - from package: qt-devel
/usr/lib64/qt4/bin/qhelpgenerator - from package: qt-devel
/usr/lib/qt4/bin/qhelpgenerator - from package: qt-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/qhelpgenerator - from package: qtchooser
/usr/lib/x86_64-linux-gnu/qt4/bin/qhelpgenerator - from package: qt4-dev-tools
/usr/lib/x86_64-linux-gnu/qt5/bin/qhelpgenerator - from package: qttools5-dev-tools

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

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