Hi Ekaitz,
When I sign-in to ArcGIS Online and try to access the item, I get this error:
[ATTACH=CONFIG]30713[/ATTACH]
I think the issue is that the item is not shared or publicly accessible. Please check your settings.
Is this a webmap or a web application? Can you view it without signing-in to ArcGIS Online?
If I add "?f=json" to the end of your URL, I see this:
[ATTACH=CONFIG]30714[/ATTACH]
It seems to be accessible to the public, but I still feel there is something not working with it if I cannot access it either. After checking your settings, I would also try publishing the item again.
-Noah