Hi Gustabo,
Sorry for the trouble with this.
We'd like to rule out if this is indeed specific to build 254 or if it is present if you role back to build 252. I understand that your computer is offline, and therefore you will need to obtain a direct installer to build 252. Do you have it archived? If not I can send you a direct link over PM.
Can you try uninstalling build 254 and installing build 252, then trying the offline activation?
In addition, can you send us your .crq file that is generated from SONAR? Instructions are here:
http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Introduction.28.html#1445928 Please send me your file over a private message. If you need a file hosting service please let me know and I can send you details to our dropbox.