You have enabled encryption for a backup archive while creating a new backup plan. When you attempt to access the backup archive and enter the encryption password, the following error message appears: "The password for the protected backup is incorrect":
Verify that you are entering the correct password by double-checking the language keyboard layout, its upper and\or lower case letters, symbols, numbers, etc. that you were used while creating the password for an encrypted backup archive(s) at the very first time.
Please note that recovering a lost password is not possible by any means. AES cryptographic algorithm that Acronis is using for encrypting the backup archives is operating in the Cipher-block chaining (CBC) mode which uses a randomly generated key with a user-defined size of 128, 192, or 256 bits, and once the password is created and confirmed while creating a backup plan, it will not be possible to recover, reset or erase it, because the password itself is not stored anywhere on the disk or in the backups. The password hash is used for verification purposes and because of that, the backup data is protected from any unauthorized access. Inability to access an encrypted backup archive is generally caused either by entering the wrong password and\or misspelling it.