OrCAD Flow Tutorial - Full Adder (Hierarchical Block Cross Reference Error)

Hi everyone, I was going through the OrCAD Capture Tutorial designing the full adder circuit using 2 half adder hierarchical blocks. My problem is when I try to cross reference the full adder design I get the following errors:

INFO(ORCAP-1399): Performing Cross Reference.

ERROR(ORCAP-1800): Duplicate Reference: U2A.

ERROR(ORCAP-1800): Duplicate Reference: U1A.

ERROR(ORCAP-1800): Duplicate Reference: U3A.

I have attached an image of the design.

Basically my issue is that each hierarchical half adder block refer to the same reference designators for the half adder schematic parts. How do I resolve this issue?  Is there a step missing in the tutorial?

Thanks for everyone's help!