How do you do that?
Your scene contains a skydome mesh with a sky material but it does not cover that part of the screen
This happened with me while creating a zoom into planet effect because I was so far out that I was beyond the boundary of the skydome mesh, so I just resized it by adjusting the scale settings and the message went away.
I notice some people had luck disabling WPO, this could be because of nanite but I think it could also be if you’re using ray tracing and the world position offset isn’t being accounted for, in this case in the skydome settings search for ‘evaluate world position offset’ and tick the box.
Awesome not fixes the issue but get a new pretty sky as well 
Thank you! That is the solution. I switched the static mesh to EditorSkySphere (SM_SkySphere also works) (to see it, make sure Show Engine Content is enabled), and also reset the location to 0,0,0 and set the scale to 10000 in x,y,z (for some reason, the default scale was non-uniform on the SkyDomeMesh that is included in the TimeOfDay_Default map).
This was indeed a quick and easy fix for disabling the notification from being shown in an UEFN viewport. However, one might want to actually see the Atmosphere in the viewport while working on the day / night sequence or other aspects of the sky dome.
I unticked Meshes in SceneCaptureComponent2D and it fixed my issue.
In my case, it was because of the Landscape Material. It was an Auto Material that had some procedural Grass and Rocks. I turned them off, and it worked.