To check for any gaps in register please go to Reporting > Reports > Attendance (tab) > Gaps in Register by Date:
Refer to - Gaps in Register by Date Report
Once in this report ensure that in the top right you have clicked to show gaps.
Error Note: If you are greeted with the below message:
You will need to go to Admin > Config > Core Set Up > Holidays to ensure that none of your dates are overlapping. For further information on removing the overlapping dates please click here.