Cross-Reference can't be updated, the story is locked.

unlock the story to proceed with the update

Can't find source document ....

re-link to the correct location or move the source document back to its original location

Can't open source document ...

somebody else is probably editing the source document

Source marker ‘...' doesn't exist in this document.

source marker was deleted or renamed breaking the connection

Source marker ‘...' doesn't exist in document ‘....

did you re-link to correct document?

Can't update cross-reference, source document ‘...' is not open.

Either open the document, or use manual update which opens the source on the background.