mopidyctl: 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/sbin/mopidyctl - from package: mopidy

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