Before I went into the developer options and switched on Stay Awake(Screen will never sleep while charging), I was receiving all of my Gmail notifications. Once I selected the Stay Awake option, I stopped receiving my Gmail notifications. I spent about 2 hours trying to figure out why I stopped receiving my notifications and finally came to this conclusion and remembered that I had turned on Stay Awake. Things are back to normal now. Is this a glitch? Can you produce the same experience by testing out what I mentioned above?