qmlscene: 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/bin/qmlscene - from package: qt5-qtdeclarative-devel
/usr/lib64/qt5/bin/qmlscene - from package: qt5-qtdeclarative-devel
/usr/lib/qt5/bin/qmlscene - from package: qt5-qtdeclarative-devel

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

On Debian possible default full paths are:

/usr/bin/qmlscene - from package: qtchooser
/usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene - from package: qmlscene

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

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