To update your Fenix Navdata to the latest AIRAC cycle, please use Navigraph Hub (Formally Navigraph Navdata Center) to update the Fenix A320 Navdata. If you do not have a Navigraph subscription, you will not be able to do this. Visit https://navigraph.com/ to purchase a subscription and download Navigraph Hub from the website.
Please note: You must go to the "Installed outside Simulator" tab to update the Fenix Navdata.
If you've updated your navdata but the MCDU shows no navdata, ensure both Fenix and MSFS are fully closed before updating your navdata.