Bip39 checksum https://writeablog.net/ipennywpzc/the-ultimate-overview-to-offline-bip39-generators-remain-secure As a consequence of how the BIP39 standard functions it is not enough sometimes to put in writing down simply a seed phrase. It's also critical what derivation path you had been working with. Sometimes when importing a seed phrase to a special wallet by another seller, https://socialupme.com/story5818673/bip39-solana-bip39-generator-secrets-https-dzen-ru-bip39-phrase-com