I think the problem is the type of the event : EntityDamageByEntityEvent try with EntityDamageEvent
Try this: <Edit by Moderator: Redacted mediafire url> put the damage you want into damage.yml
I don't understand if you want ( i make an example ): The current time is 15:01:02 and you use /mute player 15:02:00 or just /mute player 1:00:00??
try with this : <Edit by Moderator: Redacted mediafire url>
Separate names with a comma.