When something is not doing what you expect.
A few things look like faults and are not. They are here first because they account for most surprises.
There is a crop rectangle on the page. Overlays and crop rectangles use the same drag, so while a rectangle exists the overlays are left alone — and ⇧-drag selects crop rectangles rather than drawing a new overlay. Clear the rectangles with Esc and the overlays respond again. More on overlays.
Either a project window is not the front one, or you are typing. Keys like D, S, T and the arrows act on a project, so they wait while Settings or another app is in front; and they stand aside for any text field, so while a dialog is open or a lane is being renamed the arrows move the insertion point instead. Close the dialog, or bring the project window forward, and they work again. More on the shortcut keys.
It is muted, or its level is down. Open View › Show Lane Controls and look at that lane's row: the speaker button and the percentage beside it are the whole story, and both belong to the project rather than to playback, so a lane turned down exports quiet too. Folded away, the controls column shows a dot against any lane that is not at full level. More on the lane controls.
Audible scrubbing starts switched off — turn it on under View › Audible Scrubbing. It also only works with playback stopped, and it follows the pointer: dragging the playhead by scrolling the timeline stays silent until the scroll settles. More on scrubbing.
The chevron or bar at an item's trailing edge is an edge marking, and it is left off where it would cover the picture instead of marking it — on brief items, and on everything when the timeline is zoomed well out. It is also left off the last item in a lane, which has nothing after it to move and so behaves the same in both modes. Zoom in and the marks come back; the toolbar button and View › Timeline Resize Mode name the mode at any zoom. More on resize behaviour.
Removing a lane that has lanes below it moves those up, and the undo entries recorded before that point refer to lanes by their old positions. Rather than leave entries that would edit the wrong lane, ClapperBoard drops the history — including the chance to undo the removal itself. The confirmation says so before it happens. Removing the bottom lane costs nothing and can be undone. More on adding and removing lanes.
Absorbing cannot shrink the next item below a workable width on screen, and when a drag would do that it cascades instead. Because the limit is a width, zooming the timeline in lets you drag to shorter times, and Set Duration is not bound by it at all. More on resize behaviour.
The project is not marked as one. Turn on Stop-motion project under Render options. The commands stay visible in ordinary projects so the feature can be found before it is switched on. More on stop-motion.
Frame length is counted in frames, so what it comes to in seconds depends on the project's frame rate. Changing the frame rate afterwards changes every duration set that way. More on frame length.
The original has moved, been renamed, or is on a volume that is not mounted. The item says so on the timeline — Image missing or Audio missing — and carries a Locate button to point it at the file again. The same thing is on its context menu as Replace Asset, and appears only on items with this problem.
One broken audio file no longer silences the rest of the project: everything else still plays.
An orange badge counting missing files means the project refers to pages, images or audio that are not in its Assets folder. Click it and ClapperBoard says what kind of files are gone, how many, and which pages they belong to, so you can find the blank page rather than hunt for it.
Files that ClapperBoard has set aside are kept inside the project package, in Assets/.trash, for a week — arranged in the same folders they came from, so a recovered file is obvious about where it belongs. Right-click the project in the Finder, choose Show Package Contents, and look there before importing anything again. Compacting empties it of anything older than that week; nothing else deletes from it.
The badge is a warning, not a failure: the rest of the project opens and plays as usual. Individual items say so for themselves on the timeline as well, and carry a Locate button.
ClapperBoard says how much shorter and asks what to do about the shortfall. Add Silence shrinks the item to the audio it actually has and leaves a silent gap for the remainder, so everything later in the lane keeps its start time — which is what you want when the pages are timed against that recording. Shorten Lane simply makes the lane that much shorter, moving everything after it.
ClapperBoard says so rather than discarding it quietly. Usual causes are a file that is not a supported type, a PDF that cannot be rendered, or a file that is unreadable where it sits — for a file still downloading from iCloud Drive, wait for it to finish and drop it again.
Supported types are still images, PDFs and audio. Video is not imported; export frames from it first. More on importing.
The project’s own files could not be read at the moment it was asked to save — usually because the document was moved, renamed or put on a volume that then went away while it was open. Rather than write a project whose pages would all be blank over the good one on disk, ClapperBoard refuses the save and says where it was looking.
Put the project back where it was, or reconnect the volume, and save again. A failed save is recoverable; a document written without its assets is not, which is why it is refused.
The project was compacted. Compacting reclaims the disk space held by orphaned files and clears undo as part of the bargain, which the confirmation states before it happens. It also empties the set-aside folder of anything more than a week old, so recover from there first if you are going to. The badge that offers it can appear mid-session as well as shortly after opening. More on compacting.
It needs at least two systems on a page to work out the spacing, so a page holding a single system is left alone. It also skips pages that are already cropped. More on splitting a score.
It needs text it can read. A PDF with a real text layer is ideal; a scan is read by recognition, which copes with an ordinary book page well enough — running heads and page numbers included — and has more trouble with ornate type, heavy layout or poor contrast. Already-cropped pages are skipped here too. More on Smart Text Crop.
The project needs at least one image item, and at least one audio item on the lane the sync reads. With several audio lanes that is the topmost one unless the preflight sheet's Audio lane picker was set to another, so a project whose narration sits on a lower lane can look empty to it. More on choosing the lane.
The match is between spoken words and printed words, so anything weakening either end weakens it. Check that the pages are readable, and that the recording is speech — a musical performance cannot be matched at all, and a score is timed by hand instead.
Low confidence on a page is not itself a failure: a page with little text has little to match, and is usually placed correctly by its neighbours anyway. Use Skip for pages that should not be retimed, such as a table of contents. More on reviewing a sync.
Syncing adds spacer items to keep the lanes aligned, and reordering freely would invalidate their positions, so ClapperBoard asks before clearing them. Nothing is lost — running the sync again puts them back. More on applying a sync.
Without a purchase, exports carry a watermark and are capped at 720p; a larger resolution is scaled down to fit rather than refused. The watermark shows over the preview during playback too, so it is visible before a long render rather than after. More on the free tier.
The picture pass is the slow half. A coarser seek precision and a smaller resolution both help considerably, and are worth using while you are still checking a project rather than producing the final file.
A GIF cannot carry audio. Use MPEG-4 or QuickTime for anything with a soundtrack. More on formats.
That is seek precision. It sets how much identical picture is collapsed into a single long frame, which speeds up export at the cost of finer seeking. A lower number fixes it but takes longer to export.
That export is not part of the free tier. It hands over the pages as full-resolution stills with no watermark, so unlike a movie export there is no reduced version of it to give you. Buying or subscribing opens it. More on the free tier.
There is no library open. Create or open one in Final Cut Pro, and the item becomes available. More on importing.
The media was written somewhere Final Cut cannot read. It is sandboxed, so the folder has to be a real place of your own — export again to your Documents or Desktop rather than a temporary location. Note also that this is a Final Cut format: DaVinci Resolve reads the timeline but will not link the media to it, and does the same with Final Cut's own exports. More on what the export writes.
If something here does not cover it, get in touch.