Error code: 21 with droboaAccess

Hi when I try to configuring my DroboAcess domaine name I have this error :

DroboAccess registration failed.
Please try again later.
Error code: 21

Any idea ?

Thanks for your help.

Ritchie

The problem is now solveā€¦

Thanks to Tobias for excellent woks and professionalism.

Regards