hts_engine: 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/hts_engine - from package: htsengine

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

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