Unable to decrypt backup files stored in S3 or locally

Hi. I set up backups on Amazon S3. I have received three backup files. I also have access to the secret_key in my /home/user-data/backups directory. In my local windows system, I tried to open the file with gpg4win software. After trying to open the file, it asks me for the passphrase. I pasted the key from secret_key.txt file to there. This does not work as it gives error of Bad Passphrase. Am I doing something wrong?

The backups are handled by duplicity. I don’t know which encryption algorithms may be in play but it would not surprise me at all if they required duplicity to decrypt.