if your group is in a subtenant you will have to define the account ID as well.
You cannot add a server to a group, if that cloud is not available to that group. I.E - Group only has vCenter clouds, and you are trying to add a managed AWS server to the group.
@cbunge It is not subtenant. Using Morpheus Console, can add the server to the group but not through API, it is going to the wrong wrong even it has the same groupId. I have tested the API via Postman as well - same result.