I Installed Plex Media server on MyCloudEX2Ultra through the WD App store.
It shows it is running but when going on “your Medias” source after reboot it still proposing to install PMS : see the screen copies attached
Make sure you finish the setup by opening Plex using its local IP address:
http://[MyCloudEX2Ultra IP address]:32400/web
This should bring up a dialog which walks you through the basic setup (e.g. naming your server, linking it to your account…). Once the server is linked to your account you’ll also be able to access it through other Plex apps (including the hosted web app)