Thanks for the info Kelly,
Answer:
1. I would like to project in my projection (ED50)
2. The layer was created trought Arcgis Desktop in my own Enterprise Geodatabase
3. The layer was published with Arcgis Desktop using AGOL Hosted Services option
4. About scale visibilty, i am not understanding exactly this suggestion. I have made to actions, At webmap level, change the scale range of this layer to be visible, at all scales. Also at Webapp level, i have hide the scale bar. After this changes, the problem persists.
Also i have changed the basemap with a tile layer of the organization that has the same projection of the layers. But the problem persists. This basemap is now activated, but i though you cannot access to it, because is only accesible from our intranet.
I will contact support and try to obtain a solution. I will post it back later.
Thanks again for your help Kelly