em-actions.php
change line 360 $EM_Booking->person->ID
if( $EM_Booking->can_manage() || ($EM_Booking->person->ID == get_current_user_id() && get_option('dbem_bookings_user_cancellation')) ){
into: $EM_Booking->get_person()->ID
if( $EM_Booking->can_manage() || ($EM_Booking->get_person()->ID == get_current_user_id() && get_option('dbem_bookings_user_cancellation')) ){