I used the examples in the wiki but the player is not recognized. What happens? 
Examples from the wiki. 
onMarkerHit : 
  
local myMarker = createMarker(-2596.625, 579.358, 15.626, 'cylinder', 2.0, 255, 0, 0, 150) -- create myMarker 
  
function MarkerHit( hitElement, matchingDimension ) -- define MarkerHit function for the handler 
    local elementType = getElementType( hitElement ) -- get the hit element's type 
    outputChatBox( elementType.." inside myMarker", getRootElement(), 255, 255, 0 ) -- attach the element's type with the text, and output it 
end 
addEventHandler( "onMarkerHit", myMarker, MarkerHit ) -- attach onMarkerHit event to MarkerHit function 
  
 
onPlayerMarkerHit : 
  
function markerAlert(markerHit,matchingDimension) 
    if (matchingDimension) then -- Make sure the player is in the same dimension as the marker (so they're actually going into it). 
        outputChatBox("You have just entered a marker.",source,255,255,0) -- Output that they are. 
    end 
end 
addEventHandler("onPlayerMarkerHit",getRootElement(),markerAlert) 
  
  
  
  
 
Before reply please try in local.