Ok I found this myself with the help of the helpdesk and google.
- Helpdesk send me to a link on how to show more error on the website.
- Then I saw my error was "Access to the path XXXX is denied". This was related to the ClientDependency framework and was trying to access a path that doesnt exist on the server
- I discovered on google that this path was specified in the web.config so I change the path.
- Wasn't working more so I went on the server and changed the permission on this folder
- It worked.
Hope this might help someone one day!