Entering the license code and clicking "Regester/Check Status" button yields:
Last Checked Thursday 15th of March 2018 09:49:26 PM
Last Status license is not active
Please match the http protocol between your domain registered and the actual protocol.
I see on your manage domain page, the domain registered is http, but your actual domain is with https.
So delete the license first and then activate again. Make sure now the domain registered is with https.