SD Card Error "no sd card"


Feb 14, 2016
I borrowed my girlfriend's camera the other day and after snapping a few shots I put the SD card into the computer (its a mac if that makes a difference) and imported into iPhoto then when I plug it back in to the camera it says "no SD card" i try it multiple times switching the camera off and on and what not and i plug it back into the computer and it works fine, after scouring the internet I couldn't find any information on what could be the problem and I wanted to take photos the next day so I went and got another SD card and it works fine so its not the camera either, previously when my girlfriend had it I she exported her photos onto a PC so I don't know if by switching to mac ive somehow changed the SD cards formatting or something, this is my first time using DSLR cameras and cameras in general to be honest so if its some sort of rookie mistake which it probably is then forgive me.

Your help is greatly appreciated

Thank you.