I have over a 1000 pics in a slideshow and it won't upload any music to the slideshow. LR 6 Will let me choose the file but it will not show or upload in the side panel. Is there a limit of Pics in a slideshow for music uploads?????
What do you mean by "upload"? do you mean it doesn't save the music soundtrack in an exported movie? Will it not play the music when you play the sideshow inside Lightroom? What kind of sound file are you trying to use?