Old dry transfers, especially if they've been subject to heat, don't always transfer well. And, as Peteski said, old decal film can be fragile, although my Walthers and Donald Manlick decals are still good after decades. Microscale, on the other hand, doesn't always age well, even sitting in the hobby shop.
It could also be something about the "ink jet only" paper. I found, as have numerous others, that ink jet printers will NOT work with regular decal paper, while dry transfers usually do. So, it's possible that whatever is done to make ink jet decal paper keeps the DT from sticking.