Thank you for the report.
I have tested Hammer of Lorent and it appears to be functioning correctly.
The highlighted entry in your screenshot is Increased Melee Damage. This shows the sum of your character’s various sources of Increased Melee Damage. So, for example, if you equip an item that says 8% Increased Melee Damage, that 8% would be reflected there. As flat Melee Damage is a different stat, that character sheet entry will not be updated.