Does the OS recognize it? LR only shows drives that are recognized by the OS.
Please tell us the OS and LR version you are using.
I work with PC and Windos7.
Windows recognize the NAS and work without problems.
Lightroom Creative Cloud version 2015.3
In the import window, you don't see the NAS?
Is the NAS mounted to a drive letter?
Can you post a screen-shoot?
Make sure you are updated to the latest version 6.4 / CC 2015.4: blogs.adobe.com/lightroomjournal/2013/06/keeping-lightroom-up-to-date.html
Also, try to deactivate the GPU acceleration and see if this helps: https://helpx.adobe.com/lightroom/kb/lightroom-gpu-faq.html
Resetting the preferences is known to cure all sort of issues as well: http://lightroom-blog.com/2015/05/23/resetting-preferences-in-lightroom-cc6/