The security key is either invalid or has expired.
Establish a new connection. To do so, proceed as follows:
Manually log out of the MieleĀ app via Profile > Profile settings > Log outĀ ā¦.
Log in again via Login/Register > Login.
When the user logs back in, the security key is regenerated and the Miele appliance is displayed again in the MieleĀ app.