When sync asks you something
Most of the time sync needs nothing from you. When Niv can't tell what happened to a file, it stops and asks, instead of guessing. Nothing is deleted while it waits.
The sync line at the bottom of the sidebar tells you when this happens. Click it to get to the question. See Sync status.
Notes that went missing while sync was off
If files Niv had synced are gone from the folder when sync starts again, Niv can't tell whether you deleted them or renamed and edited them. Renames it can identify are followed on their own. For the rest, the sync line says on hold, and Niv asks.
<!-- screenshot: the on hold dialog with one file in front -->
For each file, say what happened if you know:
Not sure — keep both: the note stays in the Space, and any new file here becomes a new note. Nothing is deleted.
I deleted it: the note is removed from the Space too.
It's now this file…: choose the file it became; the note follows it and its edits merge in.
Keys 1, 2 and 3 answer the file in front. When many files are left, you can answer them all at once. Then choose Apply and sync.
If you'd rather look first, Hold for now keeps sync waiting. Check again looks at the folder again, after you've put a file back, for example.
Files edited outside Niv
When a file was edited in another app and Niv can't find the version it started from, it keeps the file and the shared note apart rather than merging them blind. The sync line says files to review.
In Settings › Sync › Files to review, choose Review. Read both previews, then choose:
Keep both: your file is saved as a separate private copy on this device, and the file takes the shared note's text.
Use this file: the shared note takes your file's text. Your teammates receive it, including anything removed.
Use shared note: your file takes the shared note's text.
Niv shows what each choice does and asks you to confirm before it replaces anything. Save a private copy keeps your file aside without choosing yet.
Notes waiting to join the Space
The sync line says notes need you when a note can't go to the Space until you decide something:
you marked it local only after it was queued: unmark it in Settings › Sync › Local-only files, or choose Keep it local;
it's waiting on the first-sync plan on Home: review the plan there. See Spaces.
Changes the Space refused
Sometimes the Space says no to a change, and asking again would get the same answer: the note belongs to another Space, the Space no longer has it, or you're not a member. The sync line says how many. Settings › Sync lists each one, and Forget these clears them. Nothing on your device changes.
Notes from another Space in this folder
One folder syncs with one Space. If notes here belong to a different Space, Settings › Sync says so and offers:
Use this folder only with the current Space: your files stay where they are, Niv forgets the other Space here, and the folder syncs fresh with this one;
Unbind instead…: stop syncing this folder, and use a different folder for the other Space.
Properties Niv can't read
If the properties block at the top of a note has a mistake, Settings › Sync lists the note under Properties Niv cannot read, with the line to look at. The note's text keeps syncing. Fix the block in the note, or choose Fix indentation when Niv offers it.