uplatex: 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/uplatex - from package: texlive-lang-japanese

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

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