Comment 1 for bug 1814395

The add-cloud and add-credential commands currently only operate on the local Juju client's internal YAML files. They are intended to set up the Juju client so that a *new* controller can be bootstrapped from scratch with a new cloud. These commands do not affect any running controller.

You are trying to use the commands to do something that they are not designed to do, nor is supported - add a different, new cloud to a running controller.

The error messages are indeed less than helpful. This is an area that is flagged for improvement.

Note also - Juju will be gaining the ability to support multi-cloud controllers but it's not there yet.