XQD....WTH?

I have a Nikon D4 and use a card reader to download images to my iMac. The camera came with a 16 gb XQD card, which I am still using. However, my first card reader (Sony, came with the camera) didn't seem to be reading the card and so, I purchased a new Sony reader. All was going well with the downloads, but this evening the card is not being recognized at all. The small blue light won't come on the reader when I insert the XQD card. 

As an alternative way of getting the photos off the card I decided to connect the usb cable that is provided with the camera to the computer, then to the small usb port on the left side of the D4, turned the camera on. Alas, the photos on the card are not downloading, no prompt for transfer, etc. I can see the photos on the Camera LCD. Any thoughts as to what is going on here?

Thanks, 

Yohan

Update. I tried an alternate usb ports at the back of the iMac and found that the port I was using seems a bit loose when the male end is inserted. I have been using this port for other things, external hard drive, printer, etc. Anyway, the card reader worked in a different port. I must have used the same faulty usb port when plugging in the camera directly via cable. I thought I had tried other ports initially in case this was the problem, so in my consternation I must have reused the same faulty one. Disappointing to have faulty usb ports, there is a lack of usable, accessible usb ports on this 1 year old iMac to begin with!!!

One of my two USB ports on my MacBook pro is a bit flakey like that too