Hi Alexander,
1.You company must have ReportBuilder enabled at Adobe Backend. Depending on your contract you will have a set amount of licenses available == number of usernames to which you can grant access to reportBuilder.
2.To check if you have ReportBuilder activated for your company go to Admin tools >> user management. Then go to group Management. If you Can see a group ReportBuilder then it is enabled.
3.If you want to download ReportBuilder, add your username to the group and go back to the download page, you should see the download button. Make sure to download the version 5 and the right bit version, check which version of excel you are using. (if you cannot see the download button straight away disconnect and reconnect)
Please let me know if it worked.
Best regards.
Alexis Cazes