tandem: 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/tandem - from package: tandem-mass

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