Unity Gameobjects not Rendering on Your Mobile Build? Try This.

Android

Implementing the Post Processing Stack v2 into my project made my gameobjects on Android invisible but this easy fix could solve your situation too.
1. Edit > Project Settings
2. Navigate to the Player tab
3. Choose Android
4. Expand "Other Settings"
5. Uncheck "Auto Graphics API"
6. In some cases, you may want to try and remove the list of graphic APIs(Vulkan, OpenGles2/OpenGles3)

iOS

The same problem existed by default and the following fix worked for me:
1. Check the Shader for your material
2. Edit > Project Settings
3. Navigate to the Graphics tab
4. Ensure the Shader you are using is an element in the "Always Included Shaders" variable
5. In some cases, you may want to try the Legacy Shaders instead of the Standard shader for your gameobjects to render

Hope it helps!