I had this before when a friend sent a project over to me to work on and now i’ve got it again.
I double click the audio recording and in the lower zone it shows an isolated track.
It is a glued part but shows as lanes in the lower window.
I can’t add this track as a reference for the audio alignment tool.
I have no idea what cubase is trying to do…
maybe its a “part” and not one solid audio event. try maybe to bounce it to see it as one audio event
That would be a bit of a pain in the neck. whats the point of the glue tool if it doesn’t glue.
well glue audio events in cubase makes an audio part,which is kind of Ancient cubase lanes system.bounce selection is the real glue for that matter 
Like Mozizo said. It’s an old way of working… lanes are much better for that type of editing now. If you just want to insert a small event on top of another, do so and then hit “x” and it’ll cross fade the small part “into” the underlying event.
I find Audio Parts are useful when you have a bunch of little bits of audio that are not aligned to grid lines. Making a Part out of all that audio makes it easy for the audio to all play in time relative to each other, but you can also move it around and align the Part to the grid.