Call to undefined method stdClass::display()

I’m trying to use Mappress along with Shortcode Exec PHP to create a map and then populate poi’s from some records I have in a data table. However, when I try to display a map, I get the “Call to undefined method stdClass::display()” error message. As a test, I used the code from the example in the documentation:

$mypoi_1 = new Mappress_Poi(array("title" => "DC", "body" => "Beautiful Washington, DC", "point" => array("lat" => 38.90279, "lng" => -77.037849)));
$mypoi_2 = new Mappress_Poi(array("address" => "500 chestnut st, phildelphia"));
$mypoi_2->geocode();
$mymap->pois = array($mypoi_1, $mypoi_2);
echo $mymap->display(array("directions"=>"none"));

Everything works fine until I hit that last line of code. Can anyone help me figure out what I am doing wrong? thanks.