Have a vocal audio track with a single vocal clip several minutes long.  Split clip to isolate a small section as I've seen in vids on YouTube etc.
 
Selected the split clip, but could not activate V Vocal.  V Vocal was greyed out.
 
Searched here and saw a post that said to bounce the clip first.  I did and it worked.
 
But why?  Was that a way of 'saving' the new split clip.  Is that the normal procedure when splitting a clip, you have to bounce it first?
 
I used V Vocal on this very same track the other day, didn't save any changes.  I didn't split the clip, just selected the whole clip, but V Vocal launched/worked.
 
Just curious.

You don't normally have to bounce them, but if you have something like Audiosnap enabled, V-Vocal won't work so bouncing to clip removes AS from the equation

Same with Groove Clips