Z8 files are not recognized using a card reader

Does anyone else have this issue? Adobe bridge will recognize my Z8 files and convert then to DNG IF I connect my Z8 directly to my computer with a cable, leaving the memory card in the camera. However, if I use a card reader Adobe bridge does not recognize the files. I have tried two different card readers with the same result. Let me know if you have this problem too and how you solved it. Thank you in advance for your help!