Carplay is a trademark registered by Apple. Mirrorlink is the brandname for Carplay used by Peugeot and Citroen, thus avoiding the payment of royalities to Apple just to be allowed to use the name Carplay. Technically, they're both the same, i.e Mirrorlink is Carplay and vice versa.
A Software update might be needed to activate a "flag" in the system software of your unit.
In other words, your dealer is a twat and needs to be slapped.