Identify the presentation that actually appeared
Compare the large screen with the phone or tablet. An identical mobile layout is different from a DeX desktop with app windows and its own taskbar. Record which one is visible rather than describing every external picture as DeX.
Confirm the Galaxy model supports the intended cable output and accessory. Samsung’s setup page separates cable, dock and wireless methods, with software-dependent screens. A charging connection or a similar USB-C socket is not enough to infer that every device offers the same external desktop. Keep any adapter model with the recorded connection method.
Use the matching mode control
For its documented cable workflow, Samsung says the device may first mirror the mobile screen. It then describes selecting the Samsung DeX notification, or the DeX quick-setting control, to enter the desktop environment. Follow the instructions matching the installed interface and acknowledge any first-use prompt.
The current Australian product guidance also separates wired desktop and screen-mirroring controls. Its mode-switch rules do not apply identically to wireless DeX. Keep the connection method with the menu route instead of combining a wired screenshot with a wireless tutorial.
Verify the application inside the desktop
Once the intended desktop appears, open the authorised media application there and check navigation, picture and sound separately. A desktop loading successfully does not establish that every app supports this environment; Samsung explicitly qualifies application compatibility.
Before unplugging the HDMI cable, save any unsaved work. Samsung notes that disconnecting it restarts DeX. For help, provide the Galaxy model, software, cable or accessory, initial mirroring result and mode control used. Those facts distinguish a working display in the wrong presentation mode from an unsupported output, a missing desktop prompt or a later application-level playback issue.