Hello, please make sure you are using the same platform (dlsite, itch), the correct game (SB Futanari birthday, SB, Orks Ryona BBC) and the corresponding user account. Additionally the game can be found in 'My Library' section of the itch website or via email confirmation (when purchased).
If the issue is not resolved feel free to contact me or itch.io (this sounds more like a website/platform issue rather then game itself related)
Best regards,
~NK