Microsoft 365 Tenant Migration Assessment

Is this assessment working. Getting an error on step 3 with:

"Unable to get root sharepoint site. Cannot finish authentication. Error:

Invoke-RestMethod : The remote server returned an error: (403) Forbidden. At C:\app\pkg\tasks\authenticate\authenticate.ps1:450 char:70

… $rootSite = Invoke-RestMethod -Method Get -Uri $url -Headers $header …"

Thanks