There may be different reasons, why there is no connection between the mobile device and the desktop computer. Please check the following points, first:

For testing, you can access the server in the desktop program from any browser. To do this, enter "http:<address>:<Port>" (e.g. http://192.168.178.44:8080) in the browser. You find the values for "address" and "port" in the preferences. Please close the preferences before entering.

If you enter above address, you should see the following message:

If you see this page, you tried to access this server...

You can enter the address from the desktop and from the mobile device.