All Sales orders with the Release status = Ineligible in constrained Supply Plan

Summary:

When I run a constrained Plan, in the supplies and demands table I can see all the lines with Order type = Sales order is found have their Release status = Ineligible. Will Sales orders never be triggered with a Reschedule signal by Planning automatically after a Plan run or could any setup stop the Planning engine to suggest a Reschedule signal to a Sales order?

Once I Firm the Sales order and Save the record, the Release status is updated to "Release". I am wondering if planning would always suggest only the status "Ineligible" for all Sales orders or could there be possible reasons for this behavior. Please help