E-Newsletter error after the new update

Hi,

When I click the send button to choose the groups and that stuff, I'm getting this error:

Fatal error: Access to undeclared static property: MS_Plugin::$api in /home/pama/public_html/wp-content/plugins/e-newsletter/email-newsletter-files/class.functions.php on line 641

Image one: The Error
Image two: the PHP code

Support access is ACTIVE

Thank You for always helping me!
Jose