convert_seq: 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/convert_seq - from package: profphd-utils

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

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