pn53x-diagnose: 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/pn53x-diagnose - from package: libnfc-pn53x-examples

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

Error in other languages:
pn53x-diagnose: bevel nie gevind nie
pn53x-diagnose: comandă negăsită
pn53x-diagnose: comando não encontrado
pn53x-diagnose: commande introuvable
pn53x-diagnose: command not found
pn53x-diagnose: käsku ei ole
pn53x-diagnose: không tìm thấy lệnh
pn53x-diagnose: komanda nerasta
pn53x-diagnose: Kommando nicht gefunden.
pn53x-diagnose: kommandot finns inte
pn53x-diagnose: komut yok
pn53x-diagnose: nie znaleziono polecenia
pn53x-diagnose: níor aimsíodh an t-ordú
pn53x-diagnose: no se encontró la orden
pn53x-diagnose: no s'ha trobat l'ordre
pn53x-diagnose: opdracht niet gevonden
pn53x-diagnose: parancs nem található
pn53x-diagnose: perintah tidak ditemukan
pn53x-diagnose: príkaz nenájdený
pn53x-diagnose: příkaz nenalezen
pn53x-diagnose: команда не найдена
pn53x-diagnose: командата не е открита
pn53x-diagnose: 命令找不到
pn53x-diagnose: コマンドが見つかりません