Isn't that how it is supposed to work
I don't think you have been "hacked"
I turned on Two Factory Authentication mode, it worked very well. But yesterday, I reinstalled my Macbook, and iPhone, verification code popup don't automatically display when I login new device. I must get code through text message, or manually getting verification code from iCloud setting. I logged both iPhone, and Macbook, but all don't show popup (I also try to log from another pc but same result).
I’m using Mac OS 10.12.3, and iOS 10.2.1
I think two cases:
1. It's a problem occurred when I reinstalled my device.
2. Someone (may be a "hacker") controlled my apple ID and my devices. (I'm worry about this)
Please, help me. Thanks!