Hi all,
I try to apply a custom site design via power automation to a modern SharePoint site, which is created when a new Office 365 group had been created.
When I create the Sharepoint site programmatically with the Sharepoint Rest API (see below) OR apply the site template via the Sharepoint UI then the custom site design gets applied. So I know the site design works.

But I create the site via the Graph API to have an office 365 group. In the Graph API I couldn't find any way to apply a design so I thought I just create a child flow which solely applies the design. The HTTP post to the Sharepoint site via the Sharepoint API (see below) just doesn't do anything. I spend days now researching but there is no clue why this is not working.
Now I'm here and hope someone has an idea how to solve this issue.
Many thanks,
Christoph
The HTTP post

The response I got
