How to fix the invalid signature when installing WebZap Extension for Photoshop CC?

The versions I am using are:

Adobe Extension Manager CC 7.1.1.32
Mac OS X 10.9.1

Here are screenshots for error message and preference setting:

Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.

Anyone have solution or workaround to this issue?

Thanks