https://github.com/thehcginstitute-com/m1/issues/590

app/code/community/Ebizmarts/MailChimp/Model/Api/Subscribers/MailchimpTags.php

@@ -119,29 +119,22 @@ function getSubscriber():Sub {return $this->_subscriber;}
  * @param bool $subscribe
  * @throws Mage_Core_Exception
  */
- function processMergeFields($data, $subscribe = false):void
- {
+ function processMergeFields($data, $subscribe = false):void {
  $helper = $this->getMailchimpHelper();
  $email = $data['email'];
  $listId = $data['list_id'];
-
  $STATUS_SUBSCRIBED = Mage_Newsletter_Model_Subscriber::STATUS_SUBSCRIBED;
  $storeId = $helper->getMagentoStoreIdsByListId($listId)[0];
-
  $this->_mailChimpTags = $helper->getMapFields($storeId);
  $this->_mailChimpTags = $this->unserializeMapFields($this->_mailChimpTags);
-
  $customer = $helper->loadListCustomer($listId, $email);
-
  if ($customer) {
  $this->setCustomer($customer);
  $this->_setMailchimpTagsToCustomer($data);
  }
-
  $subscriber = $helper->loadListSubscriber($listId, $email);
  $fname = $this->_getFName($data);
  $lname = $this->_getLName($data);
-
  if ($subscriber->getId()) {
  if ($subscriber->getStatus() != $STATUS_SUBSCRIBED && $subscribe) {
  $subscriber->setStatus($STATUS_SUBSCRIBED);
@@ -159,19 +152,16 @@ function processMergeFields($data, $subscribe = false):void
  $this->_addSubscriberData($subscriber, $fname, $lname, $email, $listId);
  }
  }
-
  $subscriber->save();
  $this->setSubscriber($subscriber);
-
  if (isset($data['merges']['GROUPINGS'])) {
  $interestGroupHandle = $this->_getInterestGroupHandleModel();
-
  if ($this->getSubscriber() === null) {
  $interestGroupHandle->setCustomer($this->getCustomer());
- } else {
+ }
+ else {
  $interestGroupHandle->setSubscriber($this->getSubscriber());
  }
-
  $interestGroupHandle->setGroupings($data['merges']['GROUPINGS'])
  ->setListId($listId)
  ->processGroupsData();