我尝试备份并收到以下错误消息：
Backup Failed
Error processing remote manifest (duplicity-inc.20180809T151337Z.to.20180816T192555Z.manifest.gpg): GPG Failed, see log below:
===== Begin GnuPG log =====
gpg: WARNING: "--no-use-agent" is an obsolete option - it has no effect
gpg: AES256 encrypted data
gpg: encrypted with 1 passphrase
gpg: decryption failed: Bad session key
===== End GnuPG log =====
我该如何修复这个错误？