Hi riddlereader! Have you tested if this is happening in just one song file or in all of your song projects?
As mentioned before, make sure that you have the latest build update installed for the 2019 version. You can find it here:
https://www.pgmusic.com/support_windowsupdates.htm#644 Then, try going to Options | Return to Factory Settings, and see if the notes are highlighting properly.
If that doesn't resolve the issue, please close Band-in-a-Box, go to your bb folder (usually c:\bb\preferences), and delete the following two files:
Mysetup.dk
intrface.bbw
Next, please right click on your Band-in-a-Box shortcut and select Properties | Compatibility | check "Run program as administrator" and click apply. Then just double click on your Band-in-a-Box icon to launch the program and test your song.