Parent (change request) and Child (change task) templates are configured properly but when the change request is created from parent template, the change tasks records are not created.
Jakarta Patch 10
Most probable cause is that there is a business rule with 'Abort action'
If the parent and child templates are configured properly as mentioned in this documentation,
and the issue is still seen, then there must be a business rule with 'Abort Action' in the child table that must be preventing the insertion of child records.