SureDesign is the only source from where you can get the required files. I have been through same issue in the past. It looks like you have registered in an existing workgroup. There are 2 possible conditions:
The existing workgroup was created by someone you know (your PI/colleague in your lab or a different lab within your organization). If you know that person (who will now be the workgroup administrator), then call/email him/her and ask to approve your registration request by login into their SureDesign account.
You accidentally chose a generic name of your "new" workgroup while registering into SureDesign which already exists and the administrator is a person unknown to you. In that case, send a email to Agilent support team (informatics_support@agilent.com) and ask to disable your current registration request. Then, re register with a "unique" workgroup name. By doing that, you will be the workgroup administrator. You will then be receiving an automated email to activate your account.
Since, you happened to register an year ago, your request might have already expired. So, try the registration again or try option#2 as mentioned above.