The answer
Ordinary Solana transactions reference a recent blockhash with a short validity period. Signing offline and submitting too late can leave the transaction expired.
What to do next
Use a fresh blockhash or a carefully managed durable-nonce transaction if the wallet and workflow support it.
Solscan — Solana explorer
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Ledger hardware wallet
A hardware signing device to compare for supported Solana assets; it does not fix Solana network, token or smart-contract faults.
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