Your project has to be updated time to time. To upload new data, update settings. If your project is being updated, based on your user role you will see:
Admin role sees a popup window (which can be dismissed) and a warning bar at the bottom on the project page and in the views and can still access all project's views.
Editor, Load data and Viewer roles can access the Project page, but cannot access any of the project's views.
We highly recommend when doing the maintanance of project to set the project's status to "disabled". This will display a maintenance notification to the users. Once you are done with the maintanance you should enable the project. Refresh of browser is necessary to remove the notification.
Find out more about project management in Developer Documentation.