I am having the same issue, only when I want to use the camera. It asks for me to insert an SD card. I have tried removing the card and re-inserting but is still asking for me to insert card. I have gone into settings and it says the total space is unavailable, Available space is unavailable and the options to Mount sd card, erase the sd card and sd card encryption, are darkened and does not allow me the option to do so. Where do I go from here?
It appears your device may be damanged or your using a faulty sdcard, i'd try another sdcard first, If the issue persists, Check to see if your under warrenty or have insurance.