You don't need network to test the app.,
But i bet you have to run osF as administrator and make sure the used port for the connection is open in firewall.
And the Android should be on the same network.
You must then know the IP of the PC running osF en connect to that IP and port.
All do there is this offline methode my test also uses.
It produces files you must then upload to a webserver.
Such a busy person are you the only one working on this as you are the only one that ever respondes to the Forum
Suggestion when you do get around to it dump the colour scheme, it is almost impossible to read ( tried it on my old tablet not vs Android 10)
Go to basic black and white, easier to read.
just my thoughts