I observed the following with a similar System (Kubuntu) with an external Card driver, but maybe it helps. Kubuntu will mount Card automatically if I first insert Card into Cardreader and then Cardreader into USB. Kubuntu will do nothing if Cardreader is already attached and a card inserted later.

Maybe a "mount -l" (the parameter is an "Ell", not an "one") to be typed in a terminal window will show you which device name has been given to your card after inserting, if any?