You can once again buy 
Ensemble: Chronomancer Regalia in MoP Remix!
Ensemble: Chronomancer Regalia was broken for a long time. If you bought this during the first few weeks of Remix, you couldn’t learn it. Then, Blizzard fixed the item, at the same time, updating vendors to hide items you already learned, so if you bought the bugged version that taught you nothing, you would no longer see the working version for purchase, as one player explains.
Comment
byu/Grayvves from discussion
inwow
With only a couple of days of Remix left, the ensemble has been fixed and is now available for purchase!
Remix – Ensemble: Chronomancer Regalia (Mythic) just worked for me
byu/EXB2019 inwow
If you haven’t bought the ensemble back when it was fixed, check the vendors again and get it before it’s too late!