All apps in sharepoint store are greyed out

Greetings,

I have followed all steps to configure the SharePoint Store in SharePoint Server 2013. I can open the SharePoint Store, but all applications are greyed out and I can see this error message : "Sorry, but this app is not supported by your server" for all apps. However, I have a Enterprise Licence of SharePoint 2013 ans there is not another error message, but I cannot add an app from SharePoint Store.

Thanks in advance for your answer.

Mike