xls2ods: 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/xls2ods - from package: unoconv

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

Error in other languages:
xls2ods: bevel nie gevind nie
xls2ods: comandă negăsită
xls2ods: comando não encontrado
xls2ods: commande introuvable
xls2ods: command not found
xls2ods: käsku ei ole
xls2ods: không tìm thấy lệnh
xls2ods: komanda nerasta
xls2ods: Kommando nicht gefunden.
xls2ods: kommandot finns inte
xls2ods: komut yok
xls2ods: nie znaleziono polecenia
xls2ods: níor aimsíodh an t-ordú
xls2ods: no se encontró la orden
xls2ods: no s'ha trobat l'ordre
xls2ods: opdracht niet gevonden
xls2ods: parancs nem található
xls2ods: perintah tidak ditemukan
xls2ods: príkaz nenájdený
xls2ods: příkaz nenalezen
xls2ods: команда не найдена
xls2ods: командата не е открита
xls2ods: 命令找不到
xls2ods: コマンドが見つかりません