its very well done, quite a nice portrait! I think the biggest reason it looks a little off to you still is because it doesn't quite say "link" like something that detailed and realistic should in order to look "right"
I'm not sure what its missing though, wish I could be more help!
This is great! You're definitely improving on your faces, the nose there is much more defined, the eye brows are shaping his sockets better and his eyes look nicely sunk in. Nothing better than a blue-glowy light source to give that face an extra pop