The root cause of the issue where all the Loyalty automations that have Data Processing Engine actions are failing is because the Default Workflow User is missing the CLAAnalytics Base User permission set license (B). This permission set license is essential for the Default Workflow User to execute actions related to the Data Processing Engine within Salesforce Loyalty Management. Without this permission set, the user lacks the necessary access rights to run these specific automations, leading to the observed failures. Salesforce documentation on Loyalty Management would provide guidance on setting up and troubleshooting automations, including the necessary permission sets for different actions.