sesha-add-stock: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sesha-add-stock - from package: php-horde-sesha

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