When School Cloud Systems generates an error to say no parents are linked to certain students, when you can see there are contacts on the student profile, select Contact 1 and click on the cog next to their name. 

If Responsibility says No, the data is not going to pass through in the API to demonstrate parental responsibility.

Change this field to Yes, Save the change at the base of the contacts details, then go back to School Cloud Systems to refresh the data feed. You will now find the error has gone.