nLight wired, wireless, or xpoint devices do not appear on the Updates screen for having an update available.
This can happen in a case whereby you are not connected to the Internet and are using a specific non-standard channel.
The default update channel is for Stable or standard released product.
However, hot-fixes and other site-specific updates may require using a specific update channel.
Updates using a non-standard channel does not have access to the firmware cache which is a collection of firmware updates used when not connected to the Internet.