Can't connect to Wireless pro from IOS when offline



I have a WD MyPassort Wireless Pro with the Plex server installed. It is working great on my laptop (with or without internet) but for some reason, the Plex app on my iPad only works when there is internet. I have bought the activation, and it shows in my account settings. I can also connect the Plex server through the :32400 port on my laptop offline, but when I try to get the Plex app to connect it says "Couldn't connect to server" even though I am connected to the "My Passport 5GHz" network.