I realize this has been asked in many different ways but I cannot seem to solve this according to the many different posts. I am using Unity 5.6.1 and just recently I had strange behavior where I can see my game in the Game view but when zoomed in to normal working conditions, I cannot see my game objects in the Scene view. If I zoom way out I can finally see them but cannot work with them.
I working in 2D mode. When I switched to 3D mode I noticed my Canvas was VERY far from my GameObjects. I pulled my other GameObjects closer to my canvas and everything was fine. It was then that I discovered “Plane Distance” on the Canvas properties. It was set to 100. Anyway, as I changed this value, the canvas moved closer/farther from the rest of my GameObjects.
Note: I did have all my Sorting Layers set up properly.