h2cli: 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 Debian possible default full paths are:

/usr/bin/h2cli - from package: hydrogen

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

Error in other languages:
h2cli: bevel nie gevind nie
h2cli: comandă negăsită
h2cli: comando não encontrado
h2cli: commande introuvable
h2cli: command not found
h2cli: käsku ei ole
h2cli: không tìm thấy lệnh
h2cli: komanda nerasta
h2cli: Kommando nicht gefunden.
h2cli: kommandot finns inte
h2cli: komut yok
h2cli: nie znaleziono polecenia
h2cli: níor aimsíodh an t-ordú
h2cli: no se encontró la orden
h2cli: no s'ha trobat l'ordre
h2cli: opdracht niet gevonden
h2cli: parancs nem található
h2cli: perintah tidak ditemukan
h2cli: príkaz nenájdený
h2cli: příkaz nenalezen
h2cli: команда не найдена
h2cli: командата не е открита
h2cli: 命令找不到
h2cli: コマンドが見つかりません