Can't change spouse details on amended tax return?

Is there a trick to changing the spouse details on an amended tax return?  I have a client who didn't declare that he had a spouse when we lodged his tax return.  I have gone to the original tax return and click on the A (amend) to create an amended return but when I go to the Spouse details section, it appears to be greyed out and I am unable to amend this part.  Can anyone help please? I have attached a screenshot.  I get the same problem when I click on the K and I can't select the spouse if I click on the three dots next to the K box either