This message appears in my website
Warning: array_key_exists() expects parameter 2 to be array, null given in /home/permacu5/public_html/wp-content/plugins/newsletter-leads/leads.php on line 337
No, my tip won't work, there is an error in the code (or better the code generates a warning if you have the wordpress debug mode active). I'll fix it and publish an updated version.