Warglaives not transmogging for me?

I have both warglaives of Azzinoth on my Monk which I farmed out years ago and it is not allowing me to mog them on any character including my DH.
I notice I can transmog my Shadowmourne and Dragonwrath legendaries, but does Warglaives not count?
Warglaives were usable on warrior,dk, rogue and monk before DHs were introduced.
It’s not letting me mog Warglaives on my DH.

The Warglaives of Azzinoth themselves are not transmoggable. There is however, an alternate version for Demon Hunters only.

Here is how to get that transmog for your DH:

In order to be eligible to get the transmog version (Arsenal: The Warglaives of Azzinoth), you MUST first have the Feat of Strength achievement (Warglaives of Azzinoth) from equipping both Warglaives of Azzinoth on the same character.

Then any character on that same Battle Net account can kill Illidan in the BC Timewalking version of the Black Temple and unlock the transmog for their Demon Hunter.

More info here: https://www.wowhead.com/black-temple-timewalking-loot-transmogrification-guide#warglaive-transmogrification