I have a customer using Windows 7 and the latest versions of Photoshop CC and Extension Manager CC.
I have two extension for them to install.
When they download the extensions or move them from an email to the desktop, they are automatically extracted and can not be opened in Extension Manager CC. These are extensions for Photoshop and the extracted files are showing the folders that Photoshop uses such as Assets, CSS, CSXS, ect.
I have tested this on a Windows 7 and can not replicate the issue. When I double click the .zxp file it loads into Extension Manger.
I am a Mac user so am a little lost as to why this is happening.