"copy from source media" greyed out?

Trying to import session data from another session .. all my years, I've made sure to select "copy from source media" so I can edit/delete on the new session without it effecting the original.

Now.. both "link to source media (where possible)" and "copy from source media" are greyed out.



"consolidate from source media" and "force to target session format" are my only options.



any clue why "copy from source media" would be greyed out?



Thanks