Rejections feel final, but the great majority are administrative rather than substantive. The fix is usually a better scan.
Find out the reason
The notification names a cause, even if the wording is terse. Document quality, mismatched details and an ineligible passport are the three broad categories.
Fix the specific problem
Do not resubmit the identical file and hope for a different result. If the photo failed, retake it. If a passport number was mistyped, correct it and check every other field while you are there.
Resubmit with time to spare
A second application starts a fresh processing clock. If your flight is close, move up to an urgent tier — the fee is smaller than a rebooked ticket.
When to ask for help
If a second attempt fails for a reason you cannot identify, use a service that reviews the documents before submission. A pair of trained eyes on the file is cheaper than a third rejection.