Even if you're online, periodically tapping a reference link results in 'Not Available', even though your library should produce the reference.
In the screens below, I was in Targum Neofiti and 'gehenna' caught my nefarious eye; the word is also localized to the NT gospels. The footnote linked to Jubilees 2:7, and tapping it resulted in failure (first screen below).
However, long-pressing the same link achieves the desired reference (2nd screen copy, lower panel). Can't say how reliable this tip is!

