You may have an admin from a previous event who is now a regular attendee. Follow these instructions to change their status which will also allow you to see and edit their password.
1. Go to Users and Teams > Manage Users
2. Search for the user.
3. Click on the "Downgrade Admin" icon
4. You will then get an opportunity to review the other events where this admin is found and confirm the downgrade. Click on the "downgrade admin to regular user" button to confirm and save the status.