When starting the cutscene at the top of the mountain with Lufsela to summon the stormrooks the cutscene will start and there will be no VO present in the cutscene. This will continue after the cutscene and all NPCs will not have active VO. This will occur on all of the players characters not just the one they watched the cutscene with. Fully restarting the game fixes this issue.
If anyone else is experiencing this comment and hopefully Blizz QA can get eyes on this and get a solid repro 
It’s not just that cutscene, but seemingly every one after that also triggers this new bug.
But you’re not alone in experiencing this.
I’m also experiencing this, for this cutscene and subsequent ones.
This exact issue happened with the Magni cutscene that was added as part of the brief questline in the pre-patch. Can’t believe they let it through again.
This is so disappointing. I’ve done the quest 4 times with supposed work arounds that have yet to fix the voices. I looked up the wowhead version and it’s also broken! I feel silly saying it, but this ruined my evening a little bit. Still going to keep trying work arounds, but I’ll probably give up soon and just pretend they said inspiring things!
Ya I just did a dungeon after the bugged cutscene and no voice lines were playing there either.
Had this happen to me as well, both with the cutscene at the top of the mountain summoning stormrooks and the one a little bit later where the Earthen smash the console in the Proscenium. At least with subtitles on I still knew what was happening but it really does dampen the whole experience and it shuts off ALL NPC dialogue after to boot!
Relog does fix it but it means I’m getting cutscenes without any voice if I want to continue the campaign.
Just did it. Happened to me to.
Guess I’ll wait to do the campaign until a fix is implemented.
Im having the exact same issue as well
Same here - quite annoying tbh!
do a game repair looks like it fixed it for me