No "Resend Gift" button
I sent a song to my dad as a gift on iTunes and he says he could not open the song. I wanted to try resending it to him, but the option is not available for that song. I have seen comments suggesting that the reason is too much time has passed since I gifted the song to him, but that can't be the case since another song I gifted to him long before this one still has the "Resend Gift" option available. Why is the option not available for this song, and what can I do to make it available/regift the song?
iPhone 6, iOS 8.1