DVS Signal will not go into Serato after Mac OS 10.14 (Mojave) and later if Microphone access is not granted in the Security & Privacy section of your System Preferences.

You can find that setting in the following location:

System Preferences Security & Privacy Privacy  Microphone  Serato DJ Pro

Once there, check the box next to Serato DJ Pro to enable Microphone Access.


Note: After granting Microphone access, you will need to close and reopen Serato to restore DVS functionality