PKWARE AES-128 and AES-256 algorithms are part of PKWARE's proprietary and patented Strong Encryption Specification (SES) format. Even though we could easily add support for these algorithms, we are not allowed to do this because SES is a patented technology and PKWARE refused to grant us a license:
"Regarding your request for a license for the Single Password Symmetric Encryption technology, PKWARE is discontinuing this licensing program and no further licenses will be issued under it. We are unable to grant your request." - PKWARE, Inc.
Sadly, this means that even though we could add support for PKWARE AES-128 and AES-256 within hours, we can't. Sorry!
Fortunately, due to PKWARE's licensing policies, most of its competitors use WinZip AES-256 encryption which utilizes a different file format. It's free, and it's supported by Rebex ZIP and most third-party ZIP tools (including PKWARE's). Until PKWARE change their mind, WinZIP AES-256 is the recommended format to use.
Update: In Rebex ZIP 2016 R1, the algorithm check was modified to produce a more meaningful error message: "This file uses PKWARE's proprietary encryption algorithm that is no longer licensed to third parties."