What solved my issue was nothing less than granting Digicheck access to my microphone............ ok.... no matter what, what ever rocks its boat, I'll do it.
It is done under System Preferences /Security&Privacy/click the privacy "tab" -> choose microphone -> there you should see Mixbus and Logic as well as DIGICheck in my case. All need access to the microphone.
I am on different HW so it may be specific things for those you got, but if you had it working in HS and now suddenly in Mojave there is problem to get signal in to a software, chances are you need to grant access to the microphone (I am still a bit "wow, really??" for that one).
Hope this little finding helps you as well!