User is trying to enter a credit card refund in Core, but gets prompted to select an employee or vendor.
This can happen if you have selected a contact other than an employee or a vendor in the Purchased From field and then entered activity/expense items on the Items sub-tab. Core does not allow this because on saving a credit card transaction with activity/expense items, Core automatically creates time/expense entries, which can only be associated with employees or vendors. So, if you have to add credit card transactions for contacts other than employees and vendors, you should enter them directly on the Accounts sub-tab against accounts and add a memo for reference. Check the Core Help for details.