Hi Pietro,
Sorry if this is the wrong question, but are you sure that the media is linked to the node? It should appear in the node's "Media" tab. If not, go to the Media and find the "Media Of" field. Set it to your existing node. This happens automatically if you create Media from the _node's_ Media tab (but not if you create it from the global Media tab).
Also, your Media needs to be tagged with a "Media Use" for it to display. The "Original File" tag should cause derivatives to be created, while "Service File" is usually what gets displayed in the browser as you're looking for.
If that's set up correctly, there may be something up with the display modes:
- Use your browser's inspector to see what view mode you're on. You should see something like node--view-mode-full as a class on an element. Hence the view mode is "full" or "full content" (human-readable name).
- Check your content type's display settings (at [your site]/admin/structure/types/manage/islandora_object/display) and see if that view mode (in this case "full") is in the list of configured display modes (tabs along the top). If not, then use the Default tab.
- In this view mode, is there an EVA view configured to show? You should see a whole list - probably most in "disabled" - of EVA: XXX-EVA - YYY (e.g. EVA: Media EVAs - Service File). If you just want a basic image to show up, find one of the "EVA: Media EVAs". The others are used to display files in special viewers, which aren't needed for images. Each Media EVA (e.g. Thumbnail, Service File, Preservation Master) selects only linked Media that were tagged with the respective taxonomy term in their "Media Use" field. As a shortcut, you can see the Media Use on the listing of media on the media tab of a node. So if the Media you created is tagged "Service file" and the "EVA: Media EVAs - Service File" is set to show up on the Default display profile and you're using the default display profile... then you should see your media.