Error after update

I am having a problem after updating. I am getting an error:

Fatal error: Class ‘Shiftee_Helper’ not found in /homepages/28/d224132735/htdocs/fillthatshiftfinal3/wp-content/plugins/shiftee/shiftee-basic/includes/class-shiftee-email.php on line 49

What can I do to fix this? By the way, Hello Morgan!