I can see in the Constituent Interactions that they purchased an eCommerce product for $0 (since they used a 100% discount), but it doesn't show in the Transactions tab, or when we run a Transaction report.
Article
Number:106301
Products:
Blackbaud_Luminate_Online
Zero dollar donations will not show in the Transactions tab within the Constituent's profile. You will be able to see the eCommerce purchase when you run fulfillment reports, but you won't be able to see the transaction anywhere else.