No, that's not the problem of AES key. If that is wrong, you won't able t extract any file from PAK. I extracted Alet's model in v0.34 and encountered this issue as well. It seems like the Alpha channel in "T_Alet_head_D.tga" is broken, if you view it in tools like Honeyview, it displays correctly. But if you view it inside Blender, you can only see some dot in right lower corner.
Just change material M_Alet_Head.001's blend mode (and maybe shadow mode together) to "opaque" and switch the alpha mode in Texture node from "straight" to "none" or "channel packed", I prefer "none" because the map still displays incorrectly in Image editor pane if I choose "channel packed". Finally, deleted the Texture node links to Alpha socket of Principled BSDF, whchi makes her face totally black.
The hair's blend mode needs to be changed from alpha blend to alpha hashed or alpha clip BTW, which make you incorrectly see through the hair just like her head.
Oh, Do you still remember the link to the AES key of v0.49? This thread has 500+ pages and i'm not sure if I can find it