This is what did it for me. Instead of chaking for the cookie, the plugin saved a cookie. So in displet-pop.php file I editet line 1408 from:
if ((($.cookie('displetpop_recentpop', {path:'/'}) != 'yes' && '<?php echo $_SESSION["views"]; ?>' >= '<?php echo get_option("displetpop_pageviews"); ?>') || ('<?php echo get_option("displetpop_testmode"); ?>' == '1' && '<?php echo current_user_can("manage_options"); ?>' == '1')) && urlmatch != 'no'){
to:
if ((($.cookie('displetpop_recentpop') != 'yes' && '<?php echo $_SESSION["views"]; ?>' >= '<?php echo get_option("displetpop_pageviews"); ?>') || ('<?php echo get_option("displetpop_testmode"); ?>' == '1' && '<?php echo current_user_can("manage_options"); ?>' == '1')) && urlmatch != 'no'){