flashproxy-reg-appspot: 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/bin/flashproxy-reg-appspot - from package: flashproxy-client

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