ssconvert: 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/ssconvert - from package: gnumeric

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

On Debian possible default full paths are:

/usr/bin/ssconvert - from package: gnumeric

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

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