Littlest Pet Shop Dragon reward BROKEN!

Hello,

So I get the Littlest Pet Shop achieve...150 pets..151 now actually. So I fly to a mailbox to await my Celestial Dragon reward...which never, ever, comes. I check my pet list, in case Blizz decided to just add it to the roster...nope...nothing there. Is there a fix for this? Something I need to do to activate the reward? Or is this another bug that Blizzard has yet to fix?

Please help.

I didn't find the right solution from the Internet.

References:
https://us.battle.net/forums/en/wow/topic/6714101939
Motion Graphics Intro Video

Thanks