Sibelius is asking for register or unregister Sibelius

Hi there,
I am the only user of my laptop and my program Sibelius is registered and when I want to open the program this message appears. If I click OK nothing happens and I still cannot use Sibelius. Can anyone help me please to fix this so I can start to use Sibelius ? What is this administrator rights ?
Thank you !

Message
You cannot run for the first time, register or unregister Sibelius unless you are the computer administrator. Please log in as the computer administrator and try again. (After Sibelius is registered, any user account can use Sibelius.)
OK
