Bethany,
In terms of 'refreshing' you could try deleting the Attendance activity item in the meta course and then create a new one to see if it picks up the correct enrollment information. The 'nuclear' option would be to uninstall the module (Site administration > Plugins > Plugins overview : Attendance : uninstall) which would remove the database tables, leave the code where it is and then regenerate the tables from scratch with Site admin > Notifications. This of course would delete all instances of attendance in the system (so it would probably not be an option for you) but it might result in the correct enrollments being reloaded.