Your passport generally must:
Be valid for at least 6 months beyond your travel dates (some destinations require less, e.g. 3 months — the exact rule is shown for your destination).
Have at least one blank page for an entry stamp (some countries require two).
Be undamaged and machine-readable (an intact machine-readable zone — the two lines at the bottom of the photo page).
When you upload it, use a clear, full-page color scan or photo of the biographical page: all four corners visible, no glare, no fingers covering text, and the machine-readable zone fully readable. A blurry or cropped scan is the single most common cause of delays.