The new shopping cart allows users to pay for multiple RSVPs in one transaction, but that may make it harder to see who has paid for an event if you are used to looking in your default money account for your unit. The reason is because where there used to be individual transactions for each RSVP, now there are only two - one for the gross amount of the purchase and one for the fee.
What should you do?
Thankfully, there has always been another way of seeing who has paid for an event. Just go to the event details then click Attendance -> All Payments and you can see it there.