I have someone in the database with two different email addresses. Is there a way to combine the entries so that they are only using one email?

Although you currently can’t merge two Participant records, you can transfer slots from one Participant another. Under the Database > Participants tab, find the Participant with the email address that you want to merge with another one. Click the More… button to the left of the Participant. Click Transfer X’s Slots Someone Else. Select the To Participant. Click Transfer. Once the slots have been transferred to the other Participant, you can remove the one without slots.