First of all you need to check is virtual cam installed or not. Go to the app's preferences and select Virtual Camera from the list.
If you see this screen, then you need install driver. Please click on Install Driver button.
If you see this screen, then you need to turn ON switch Enable stream to virtual camera
If you see this screen, then write us on [email protected] email and ask to connect you with a technical support in a messenger (Skype, Telegram or Viber).
The best solution is uninstall virtual camera driver from the preferences in SplitCam.
If SplitCam already deleted and you won't install it again, then just remove the SCVirtualCamera.plugin bundle at path /Library/CoreMediaIO/Plug-Ins/DAL (open Finder window and press together Cmd + Shift + G, type this path in to the text field and press Go button). It's ok if system will ask you admin/root password, it's because driver installed in system folder.
Ofcourse you should restart macOS to take effect.
In case If any solutions above did not help you and you still see SplitCam virtual camera driver, then you need write us on [email protected] and describe your situation in details.