Ok, brief description of version numbers this is happening in.
Nextgen Version 2.0.27
Wordpress Version 3.6.1
Chrome Version 29.0.1547.76
A client gave me a ring yesterday as she was having difficult attaching a nextgen gallery to a post. I logged in on my machine to her websites dashboard and the button appears (latest versions, chrome & Windows 7).
I then did a remote connection to my home computer and logged into her dashboard and the button appears (latest versions, chrome & windows 8)
I've checked for updated on the browser and it is the lastest version. Got her to clear the cache on her computer, but still the button doesn't work.
I'm sort of stuck as to what is causing the issue and have came here for help!