KillAura only attacks entities that are ticked as combat targets, and that list isn't inside KillAura — it's the global Targets setting (alias "Enemies"), shared by every combat module. Open that and make sure Players is ticked, or just run .targets combat Players. It's on by default, so if you're on defaults it should already be set.
If Players is ticked and it still does nothing, the usual silent blockers are:
AntiBot is filtering the player out (turn it off if the server has no bots).
The player is on your friend list — friends are never targeted.
Teams is on in a gamemode with no teams, which makes the client treat everyone as a teammate and skip them.
Also make sure KillAura itself is actually toggled on — it's off by default.
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