C# Unity Main Menu Scene is Blue when played

When ever I play my game I recently created a new main menu and when I play it the scene is just blue it even shows by camera preview how can I fix this?

Have you used the Right Click > UI to create that menu? If not, it could be to do with your camera Z index. Camera are on -10 normally, and if for some reason your content is the same or less than that, it won’t be able to see it. If however this is a UI Canvas, I’m not sure. Perhaps you’ve enchecked the enabled box.