Good morning, Andreas.
Thank you for your reply.
As I mentioned earlier, I checked your website and confirmed that you have not created any standard SP Page Builder pages. Instead, your content has been built using SP Page Builder integration within Joomla articles. These articles do not appear in the SP Page Builder → Pages list, as they are managed through the Joomla Articles section.
You can find more information about this here:
https://www.joomshaper.com/documentation/sp-page-builder/integrations
For example, your homepage is a Joomla article named "Home". Please go to Content → Articles, search for the Home article, and open it. You should see the Edit with SP Page Builder option there, which will allow you to edit the page using the Page Builder frontend or backend editor.