The HCP Credentials field on a Sample Order transactions record should be populated by the same value found in the Credentials field on the Accounts object.
There is an out-of-the-box Field Level Security (FLS) setting which is required. This includes: Credentials_vod__c on the Sample_Order_vod__c object. It gets stamped with an HCP credential value (Examples: MD, DDS, etc.) taken from the Accounts object by a built-in Veeva process. This is important for compliance purposes.
The user needs FLS Read permission to the Credentials_vod__c field on the standard Salesforce.com (SFDC) Accounts object, and FLS Read and Edit permissions to the Credentials_vod__c field on the Sample_Order_Transactions object.