Top link needs a sign up to that forum, you might want to change that.
Won't be able to give a full crit until I see the subject but some early thoughts,
Well firstly, some great tech around the eyes cheeks and forehead.
The lower half of the face seems to be the area that's getting problematic.
It's a little unbalanced shading wise compared to the top half, If you flip the canvas hopefully you can see what I mean.
Small nostrils, or at least large septum.
The lips look very straight flat and unusual.
His face is upward tilting, but the straight mouth seems to flatten that angle out. As too does the beard, I feel like at this angle a small amount of the lower jaw should be visible. And even obscured by the beard, the connection between neck, jaw and head should be hinted at.
Neck seeeeems a touch thin
Though keep in mind I'm saying all that as general advice, I might be off as I haven't been able to see the portrait subject yet.
Looking forward to progress, your pixels are always a joy to watch.
EDIT:
Just saw the photo, you need to work away some of those strong shadows, they are making him look 20 years older!
With the photo in mind his chin is actually the closest thing to the camera, so ignore my advice about the underside of the jaw. Simply work on establishing and strengthening that jaw shape more,atm it looks a little like you were going for a partial neck beard.
The space from the edge of his eyes to the hairline is pushed a little to far out. Maybe trim that back and push the hair out, it look like this guy is balding presently.
