After updating to macOS Sierra, the OS no longer seems to automatically authorize network-mapped folders on system login. I have mapped NAS drives to connect to on startup, using System Preferences > Users & Groups > Login Items.
Keychain does save the login information, but it only appears pre-filled, and the network locations aren't automatically mounted on start-up.
So every time I boot the machine, I am presented with a "Connect" dialogue with pre-filled passwords.
In El Capitan, there was no need to manually authorize mapped network locations.
I don't know if changing to an iCloud-based Keychain and Two-Factor Authorization in conjunction with the Sierra updated changed anything.
I have tried removing the mappings from Login Items and adding them again, as well as rebooting etc. I have tried this on two separate computers and I have the same issue on both.