If this is not solved yet, try this:
addCommandHandler("mute",function(player,command, target)
if not(target)then outputChatBox("SYNTAX: /"..command.." [PlayerName]", player) end
local target = string(target)
local playerName = getPlayerFromNamePart(target)
if(playerName)then
local targetAcc = getAccountName(getPlayerAccount(playerName))
if(hasObjectPermissionTo(player,"command.aexec",false))then
if(targetAcc)then
local mute = setPlayerMuted(target,true)
if ( mute ) then
setAccountData(targetAcc, "muted", mute)
outputChatBox(""..targetAcc.." has been muted!", player)
end
end
else
outputChatBox("Sorry, you don't have permission to mute a player.",player)
end
else
outputChatBox("Sorry, that player name doesn't exist.",player)
end
end)