myproxy-admin-load-credential: 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 CentOS possible default full paths are:

/usr/sbin/myproxy-admin-load-credential - from package: myproxy-admin

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

On Debian possible default full paths are:

/usr/sbin/myproxy-admin-load-credential - from package: myproxy-admin
/usr/lib/debug/usr/sbin/myproxy-admin-load-credential - from package: myproxy-dbg

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