Hey DJ Bobby White,
On the top of your NS7II, above each of the channel faders there is a switch with routing options. To play tracks through Serato DJ these switches need to be set to "PC".
The grey waveforms mean that you have possibly switched one of these over to another option such as "MIC" or "LINE", these options are used for playing an external source of audio, like an ipod etc through one of the inputs.
If you still have trouble after switching back to "PC" get in touch with our support team:
support.serato.com
Sam