DSS6 Lite Product activation

Getting simple error on online product activation: Internal system error...

Telnet to activation-key.com port 25 or 10444 is working, from cli console ping activation-key.com is ok. Downloaded hardware stamp file and sent it to activation address as plaintext mail and only attachment included. Got answer:

Activation error.
Invalid attachment file. Preactivation file was not found in e-mail attachments
Please attach a valid preactivation file and send it to activation@activation-key.com .

Model: Data Storage Software V6 Lite
Version: 6.0up75.8401.5377 32bit
Release date: 2011-05-06

3 days left...

Try to send it once more today and I will check for you.

Thanks. Now got registering file back.