Hi,
The URI for updating the project default permission for Workbook and Datasource sections is incorrect. I got the following error:
404003: Resource Not Found
Unknown resource '/3.6/sites/cf5e5d82-ddba-4df4-b595-59db361ab0db/projects/b0ee5d45-6ed3-4514-b6b1-8fcd92b3969b/default-permissions/workbook' specified in URI.
It seems like an "s" is missing in the URI for Workbook and Datasource.
The correct URI are:
/api/api-version/sites/site-id/projects/project-id/default-permissions/datasources
/api/api-version/sites/site-id/projects/project-id/default-permissions/workbooks