The file was created in a later version InDesign than your version of InCopy
Just do idml file from indd in new version. And open this idml in old.
you can ask users of InDesign to help, if you not have new version.
That’s not going to be much help with InCopy and we have no idea how far back the saving will need to be done.
This can’t be done in a vacuum.
Who say that not work? Just do indd new - idml - save as old needed version indd.