Also, another setting to try is turn on Airplane mode.
The logic and reasoning is, if that is one of the iPads with cellular data service, then sometimes even when connected networking to the WIU- the app data stream goes out to the internet over cellular instead of down the wifi to the WIU.
Turning on Airplane mode forces the device to only allow wireless network, thus forcing the app data packets to the WIU connection.
Especially true for when using a Phone, but can be true for tablets.
