Need help with Breaching the tomb

I have been struggling for WEEKS now trying to do Breaching the tomb Achievement, to move on to getting the quest lines for the class mount for Warlocks. I’m stopped at Champions of Legionfall. I’ve completed the first 6 quest lines, in Breaching the Tomb. Next is to get the quest line for Champions of Legionfalls. I should be at An Urgent Message in Dreadscar Rift. Shinfel Blightsworn has no quest for me. I have gone back and checked A Glorious Campaign. All are completed except 1 that is no longer offered and can’t be done. Heroic Weapons I have them all. I have completed Armies of Legionfall and Assault on Broken Shore achievements. As far as I see I have not phased yet either. Oh, and on my way to doing Breaching of the Tomb I have already gotten Good Suramaritan. Can anyone please help. My goal. I’m after the class mount. Ive asked blizzard, but all i get is there is nothing wrong with the server no bugs. Also they said i need to complete breaching the tomb to get the class mount. they werent helpful.