I have the exact same issue as you! I posted a thread in hope someone could help (Bugged quest - Through the shattered sky).
I have been contacted by 3 GM’s after sending 3 tickets and the solutions on offer did not help at all. Their latest response I will post here -
After reviewing your issue, I believe that you can’t complete quest " A Chilling Summons" & “Through The Shattered Sky”.
After doing a little investigation here, we are aware of this issue as I have found similar issues regarding to this case. As of right now our development team is currently investigating the case right now and we will come back with an answer and resolution as soon as possible.(ﾉ◕ヮ◕)ﾉ*:･ﾟ✧
As for the “Through The Shattered Sky”, I have found out that our developers have fixed the issue that was causing this problem. Please try again. For this quest please try to leave party sync/group and abandon the quest and retake it.
Not sure they realize you cannot abandon the quest at all, and leaving/joining party sync does not work.
Such a weird/annoying issue and one I have never encountered in wow. I played during classic, skipped a few years and played cataclysm and now hoping to pick it up again during Shadowlands.
The fact I wasted money on a boost + 3 month subscription kinda burns too lol. Anyway I submitted a bug report and put in a ticket for a refund, hopefully it goes smoothly.