Are you sure your phone is connected to the whole home wifi and not the BT Hub (if you have left wifi enabled with the same SSID?).
I am sure that all the devices in the house are connected to the whole home wifi. The app does not connected to the whole home or the home hub wifi
Just purchased the disks today.
Setup was OK using Android app and have upgraded discs to v1.02.04 build10 firmware.
Have changed my SID, password and admin password successfully.
However the Android app NOW fails to connect to the discs (have tried re-installing app and rebooting the main disc)
Also, so far, by DNS is not resolving http://mybtdevice.home/ on my network either, but luckily I can administer the discs using it's IP address so that's my only current option for monitoring their status.
I had the same problem and restarting the system using the web interface cured it.
Is the device you are using to access mybtdevice.home connected to the WH wi-fi, you can only resolve the address if you are connected.