CreateFolderV2 sharing_info shared_folder_id empty

The /2/files/create_folder_v2 endpoint doesn't create team (or shared) folders. It just creates normal folders. Accordingly, the resulting folder won't have a shared folder ID, since it isn't a shared folder. Only team/shared folders themselves will have that set. It can be used to create normal folders in a variety of different contexts though, such as inside a team folder, team space, shared folder, or user's private folder. So, you can instead check 'sharing_info.parent_shared_folder_id' to see if a parent folder of it is shared.

If you want to create a team folder in a team that isn't using the team space configuration, and you're using a Dropbox Business API app with the "team member file access" permission, you can use the /2/team/team_folder/create endpoint. For teams using the team space configuration, you would just use the /2/files/create_folder_v2 endpoint to create a folder inside the team space.

Or, to just create a shared folder, you would use the /2/sharing/share_folder endpoint.

I recommend reading the Namespace Guide and Content Access Guide as they go over some of these concepts in more detail.