Just an update on my experience with this. I'm on an HP Elite X2 G3. (HP's Surface clone) and a OnePlus 5t android 10.
I select text with the pen and no highlight appears. I select text with the mouse and cursor, then click the highlight button, no highlight appears. Yet when I select text with the mouse and cursor and right click, the pop up context menu says there is a highlight, but the colored highlight isn't showing up over the text. When I go to my Android Gospel library(GL). The highlights made in Windows GL show up there. If I interact with the highlights or I make new highlights in Android GL, after a few minutes they show up on my Windows GL.
A new weird bug popped up yesterday and persists today.
I select text in a paragraph with mouse and cursor, but when I click the highlight button, it highlights everything from the selected text to the end of the whole chapter, well beyond my selection. (Of course I can only see this when I go to Android) This is random and doesn't occur every time, but I tested it, selecting text very carefully and ensuring only one verse is selected, but when I get to android, the whole chapter beyond my selection is highlighted.
My workaround has been to just highlight on my phone.