Unable to add the line while responding for the Negotiation

Summary:

We are not able to add the new line while providing supplier response for the negotiation. System is not allowing us to add new line (not alternate line)

1.Supplier should be able to create a new line ( not alternate line to existing lines) with response price as 0. And also he should be able to respond to few lines ( Not all lines)Currently this is not happening. Kindly let me know that how we can add the line.

Version (include the version you are using, if applicable):

25A