New iMac wont allow External USB card readers to mount
My 27in late 2013 iMac using Yosemite 10.10.1 will not recognize USB card readers. I've tried 3 different card readers and even a brand new 3.0 reader. I only Lexar Professional Compact Flash cards, so I have to use an external card reader. My 2010 Macbook Pro has no problems reading all 3 of my external card readers. If I plug in an SD card to the external card reader nothing happens, but if I insert the SD card straight into the iMac it can recognize the card immediately. What am I doing wrong?
iMac with Retina 5K display, iOS 8.1.1