A participant entered a multiple registration. Their credit card was charged twice for the registration, but only one of these charges can be found in Bookkeeping > Manage Initiative Records for reversal. both charges can typically be found through the Payment Details report, even through neither are listed through the event or the contact record.
Chat with Support and reference this article. Please verify the following: The second charge shows in the the Payment Details Report (you may need to filter on card holder's name) The second charge does not show on the contact record The second charge does not show through the initiative