tlsdate-helper: 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/tlsdate-helper - from package: tlsdate

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