There is no activation.
When creating the project, please select the default server www.soscisurvey.de and the the option for free use. SoSci Survey will then ask a few questions about the nature of the project, and if the conditions for free use are met, you can create the free project.
As far as I can see from your account, you have created a test project for now. You can convert this into a free project in the project settings with th pen-and-pad symbol behind "project background".