Hi Ponga,
Thank you for your interest in Syncfusion Essential Studio.
For the v5.1.1.47, the key is different from v5.1.0.50.
If you have the current valid subscription, you can retrive the key for the v5.1.1.47 from the below location using your DirectTrac login.
https://www.syncfusion.com/Support/DirectTrac/user/downloads.aspx
If you are not able to get the key from here, please email to
salessupport. They will update you with detailed information.
Please create a new DirectTrac incident if you have further queries.
Regards,
Nanda