When does the 'Confirm Sync' button appear? Why can't I see it?

'Confirm Sync' only appears when three conditions are met simultaneously: (1) your copy is 'In Discussion' (sent with no unsent changes), (2) the other party sent you a new version (marked 'Update Notification' in the list, marked 'Changes Pending Sync' in the details page), and (3) the version from the other party is identical to your current copy. In other words, both parties have reviewed it and the content is aligned. Pressing 'Confirm Sync' means 'I accept this version'. When both parties press 'Confirm Sync', this round of negotiation ends (the list shows 'Both parties confirmed'). Common reasons you can't see it: you have unsent changes (send first), or there are still differences between the two versions (open 'Diff View' to resolve differences and then send). The button does not appear for archived or canceled documents.