Nikon d810 and CF card Q

First off i'd just like to say hello to all as it's my first post on this forum.I have a d810 and when i want to transfer the files on my compact flash card(Lexar Professional 1066 UDMA 7) it doesn't transfer like it does when the images are stored on my SD card.
Any ideas?
Great forum guys

Well you need to provide more information than that on the files. Usually something like this is explained in the manual.
Is one slot capturing RAW data files (NEF) and the other jpg?

Thanks for the reply mate.I've just figured it out.I had slot 1 selected but the CF card is considered to be slot 2 (in Nikon transfer0 and when selected allowed me to transfer the files!!Thanks