my Mac does not see my usb connection to a Kindle
I am trying to move pictures from my Mac to my Kindle via a USB connection. The Mac does not acknowledge it being plugged in. Other USB devices seem to work fine. I think this may be related to my having taken the Yosemite download a short time back. I have tried everything relative to the Kindle. It now comes down to the MAC. Help please.
iMac (21.5-inch Late 2009), Mac OS X (10.6.8)