To check this error - go to the Student Profile and their Conduct tab. Click on exclusions and choose the Exclusion shown, click on the edit button and confirm that the dates entered are correct.
Autumn Census 2020:
Start Date must be a valid date between 01-09-2019 and 31-07-2020
Spring Census 2021:
Start Date must be a valid date between 13-04-2020 and 31-12-2020
Summer Census 2021:
Start Date must be a valid date between 01-08-2020 and 04-04-2020