Dreamweaver CC 2017 does not automatically save open documents if you retain preferences while upgrading from Dreamweaver CC 2015 versions.

Solution

Download the fix for your operating system and follow the instructions here to apply the fix for this issue.

Fix for Dreamweaver on Windows

Extract the compressed file. Then:

1. Quit Dreamweaver.
2. Run the .bat script with administrative privileges.

Auto save is now enabled in Dreamweaver CC 2017.

Fix for Dreamweaver on Mac

Extract the compressed file. Then,

1. Quit Dreamweaver
2. On the terminal, run the following command:

sudo sh <path to the script>

Auto-save is now enabled in Dreamweaver CC 2017.