I am now on my 3rd Sandisk Extreme Pro UHS-II SD Reader/Writer. It shows in System Report as "SanDisk SDDR-329 USB device". It works intermittently with some cards, and not at all with others. When it doesn't work the reader shows in system report as a USB device, but the card itself does not show in disk utility or the finder. The results are the same whether I use either of my two Satechi USB 3 hubs or whether I connect directly to my late 2013 MacPRO running 10.10.5. A SanDisk 64GB Extreme PRO SDXC UHS-II 280 MB/s Memory Card is NEVER seen. A SanDisk 32 GB Extreme Pro 95 MB/s may or may not be seen A Delkin 32 GB 95 MB/s card doesn't seem to be seen I have used a Sandisk Micromate for years on the slower cards and have never had a problem. Sandisk Failure Analysis has looked at my returned reader and say that it works fine in their lab. They gave me their number, so I'm trying to see what I can do on this end to see where the problem is. I'm wondering if there is something unique about the late 2013 MacPro that may cause the problem?