In a recent blog post I explained why APIs used to be completely frozen once they were published, and how we have loosened that restriction for Public APIs. Similarly, we did not allow Client Apps to be changed and then re-registered. This was never a good decision, since the Client App does not have anything "connected" to it (the way that an API may). So we should never have restricted the registration of a Client App!
When Can I Re-Register?
A Client App can be re-registered to the Gateway whenever it has been modified, or if it has been un-registered (is in the Retired state).
How Do I Re-Register?
When you have made some changes to your Client App, you can re-register it by clicking the Re-Register button in the UI.
As soon as you’re comfortable with the changes you’ve made to your Client App, simply click the button, and you should be all set!