Why is Set Primary Copy option dimmed when selecting a "offsite tape" copy ?

Hello,

I  need to restore data from tapes that had been duplicated and placed in offsite. The Primary Copies which initially stored in NBU appliance had expired. I went to the Catalogue Window, search for the copy 2 image, select that image and right-click, I see the "Set to Primary Copy" is dimmed. Can someone please advice me why is this so and what can I do so that this option is available ?

1) Primary copy in nbu appliance expired

2) Need to use secondary copy that duplicated in tapes to restore data.

Is this option "Set to Primary Copy" grey out because the Primary copy which initially stored in nbu appliance had expired some time ago, thus the backup image in the tape is now the only copy and I can restore from the offsite tape now ?

Can someone be kind to advice me ?

Thank you