I have a bit of a peculiar problem with my D7200. Manual mode my flash won't pop up when I push the button until I start to twist off the lens. I don't know how the lens is possibly interfering with the flash, but that seems to be what's going on. Also if it does pop up, it won't always go off even though all the settings say it should.
It doesn't happen consistently enough to send it in yet, but I was just curious if anyone had any input, or possible explanation.