In Photoshop CC I have no 'Extensions' menu under Window. I get Arrange > Workspace > 3D then everything else. I've searched and heard of it being greyed out but not missing entirely.
Extensions manager has been used properly to install my extensions, and I've manually checked everything is where it should be. I ran the manager as admin.
This is on a PC, W7 Pro 64BIT, CC is all up-to-date. PS version 14.2.1 (14.2.1 20140207.r.570 2014/02/07:23:00:00) x64
Because extensions in Photoshop CC 2014 are being rewritten from flash to html, all extensions in CC won't work in CC 2014.
You have to install CC 2014 compliant extensions. Your extensions menu is greyed out because are none.
Go to your Photoshop CC 2014 Help menu and click on "browse add-ons". You will be directed to the Extensions webpage.
Pick and install a CC 2014 compliant extension like Kuler CC 2014,and it will show up in your extensions menu.
The problem is not that the menu is greyed out, it's not there at all.
When I add CC2014 extensions I still don't get any extensions menu.
Have you installed the latest version of Adobe Extension Manager CC? It's 22.214.171.124.