If the Proof Is Missing or the Order Is Still Pending
A restored wallet may not retain the locally stored key for an older outgoing transaction. Check the original sending wallet's history or the platform that initiated the withdrawal; do not create a new payment merely to “retry” a missing proof.
If the transaction checks out but the exchange order is waiting, inspect its confirmation count, deposit amount and processing status. For a wallet receiving the payout, the XMR receiving guide explains sync checks. Keep the order ID when contacting support, and start at the exchange home for a new order.
See Monero's official payment-proof walkthrough and wallet RPC documentation for verification behavior.