Del,
still can't understand why you're having this issue. I use RGB .tiff files all the time. Never had this issue. As I mentioned to you before, I occasionally forget to delete any alpha channels, as this seems to cause problems for the RIP. I also recently discovered that if I don't select an output profile, I also don't get a print. (forgot to select one.) the software seems to select the one at the top of the list by default, but it doesn't print. However, I have never had an issue with the software recognizing files. Puzzling...