Provisioning a Teams Template with a specific folder structure with the PNP provisioning engine in PowerShell

Question

I try to create a template for Teams with a specific folder structure, e.g.

General -Folder 1 -Folder11 -Folder12 -Folder 2

I managed to create a Team with PNP so far, but I'm struggeling to connect it to the right SharePoint site. I get the following error message:

WARNUNG: Teamifying site at URL - https://{tenantname}/sites/testmatthias3 failed due to 
an exception:- Exception while invoking endpoint
https://graph.microsoft.com/v1.0/groups/d738ccee-e1e5-4e5f-bac8-723686716240/team.
 WARNUNG: Teamifying prompt couldn't be hidden at site at URL - 
 https://{tenantname}.com/sites/testmatthias3 in App-only context 

This is my PowerShell code so far:

$tenant="{tenantname}.onmicrosoft.com"
$Clientid= "989abaac-bf99-49ae-9dbd-dc83e9b14a1e"
$thumbprint ="B971C3CA8D6455D51238336EFAD50F5F151CFFD2"
Install-Module pnp.Powershell

# Connect to the target tenant with app-only context
 Connect-PnPOnline {tenantname}.sharepoint.com/ -ClientId $clientId `
   -Thumbprint $thumbprint -Tenant $tenant

#Apply the tenant template
Invoke-PnPTenantTemplate -Path 
 "C:\Users\...\Desktop\...\TemplateTeams.xml" 

I can't find the error.

I hope you can help