A reason is always given. Which path you take next depends on what that reason says.
Something was incomplete or didn't match — correct it and send it again. It's reviewed from the start. Repeated resubmissions eventually route you to appeal instead, rather than allowing indefinite retries.
You believe the decision itself was wrong. An appeal goes directly to a human reviewer, not back through the same automated check.
Resubmissions and appeals are tracked against your account, so a reviewer has the full history in front of them, not just a single attempt.
Prefer to understand the check itself first? See how verification works.