Really great model. Looks really strong. Finally a Not-Arthas-Deathknight!
One thing: The name of your portrait file is not 100% in sync with the main file.
Either the -ed of Mounted is missing in "Death_Knight_Mount.mdx" or the "Mounted"-ed is too much in "Death_Knight_Mounted_Portrait.mdx".
If you do not adjust this manually in the asset manager, it will not load the portrait correctly in-game.
Edit, 02.04.:
I've only seen and changed that now:
Was my post with you for so long about other things not related to the model as indicated for me?
I didn't write that. Where did that come from?