idn2: 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 CentOS possible default full paths are:

/usr/bin/idn2 - from package: libidn2

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/idn2 - from package: idn2

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

Error in other languages:
idn2: bevel nie gevind nie
idn2: comandă negăsită
idn2: comando não encontrado
idn2: commande introuvable
idn2: command not found
idn2: käsku ei ole
idn2: không tìm thấy lệnh
idn2: komanda nerasta
idn2: Kommando nicht gefunden.
idn2: kommandot finns inte
idn2: komut yok
idn2: nie znaleziono polecenia
idn2: níor aimsíodh an t-ordú
idn2: no se encontró la orden
idn2: no s'ha trobat l'ordre
idn2: opdracht niet gevonden
idn2: parancs nem található
idn2: perintah tidak ditemukan
idn2: príkaz nenájdený
idn2: příkaz nenalezen
idn2: команда не найдена
idn2: командата не е открита
idn2: 命令找不到
idn2: コマンドが見つかりません