Hi Goutham,

On assumption that you are getting this error in Studio pro, this can be because Atlas_Default layout is been deleted/excluded from project (this layout can be found under Atlas_UI_Resources module > _Layouts > Responsive > Atlas_Default). If you removed/excluded Atlas_Default layout intentionally then make sure to select alternate layout for the error page and your error should be resolved. If this layout was removed/excluded by mistake then you need to add it in your project. You can download Atlas_UI_Resources module from app store again and your error should be resolved automatically (if you made custom style changes in your project then download this module in a test project, export and import the Atlas_Default layout into your project).

Hope this helps!