I have a MongoDB Atlas cluster within which I am trying to simply copy a database within the same instance. Unfortunately, every time I try to run db.copyDatabase() or copydb ad
this error is because you are trying create the colecction above admin, in atlas this isn't possible because securty.
in this case you need to use the word key use [collection_name]
this is the link for this answer.
it is in spanish.
https://victorroblesweb.es/2016/12/24/crear-una-base-datos-mongodb/