It appears that the latest version is a major upgrade over the previous version of the software and that is why the key is not working. It is advisable to upgrade to the latest version of the software. 

To upgrade your copy of software, please contact Stellar technical support at following numbers (keep your order number handy):

Location

Technical Support Number

USA (Support)

+1-732-584-2700

Europe(Sales & Support)

+44-203-026-5337

Australia & Asia Pacific (Sales & Support)

+61-280149899

Netherlands (Sales & Support)

+31-208-111-188

Worldwide (Sales & Support)

+91-124-4326-777

Skype Id (Support)

stellarsupport

Email

support@stellarinfo.com

In case, you don't wish to upgrade, you need to use the previous version of the software (the version for which you already have the key).