xlsx2csv: 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/xlsx2csv - from package: xlsx2csv

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

Error in other languages:
xlsx2csv: bevel nie gevind nie
xlsx2csv: comandă negăsită
xlsx2csv: comando não encontrado
xlsx2csv: commande introuvable
xlsx2csv: command not found
xlsx2csv: käsku ei ole
xlsx2csv: không tìm thấy lệnh
xlsx2csv: komanda nerasta
xlsx2csv: Kommando nicht gefunden.
xlsx2csv: kommandot finns inte
xlsx2csv: komut yok
xlsx2csv: nie znaleziono polecenia
xlsx2csv: níor aimsíodh an t-ordú
xlsx2csv: no se encontró la orden
xlsx2csv: no s'ha trobat l'ordre
xlsx2csv: opdracht niet gevonden
xlsx2csv: parancs nem található
xlsx2csv: perintah tidak ditemukan
xlsx2csv: príkaz nenájdený
xlsx2csv: příkaz nenalezen
xlsx2csv: команда не найдена
xlsx2csv: командата не е открита
xlsx2csv: 命令找不到
xlsx2csv: コマンドが見つかりません