Dropbox discontinued support for iOS 8 and below. I have no control over this at all. In fact the Dropbox app itself doesn't run correctly.
I do support V2 with unrealBook, but since unrealBook one runs under iOS8 and below there's nothing I can do.
I've publicly complained to them and so have others. I put in a lot of work to support Dropbox only to have them kill it for older versions of iOS.
Complain to them - not me. I did all I can.
You can still share a set list and all files using the + button in the set list toolbar to email the file to your older iPad. unrealBook one will then unzip the file and overwrite any old versions with the new set list.
And you can still use iTunes for file sharing.