DW CC (13) uses new extension file types ZXP. Older extensions won't work in CC unless you convert them to ZXP from CS6 (12) or go to your Extension Developer's site to see if they have ZXP replacements.
I am using ZXP types. They've worked previous to a recent Dreamweaver update. All of a sudden, not go. Extensions disappear. I've had a similar problem where following an update, some of my Photoshop plugs-ins went missing, requiring me to reinstall them.