seqretsplit: 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
/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/seqretsplit - from package: emboss

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