There are several reasons why you may be experiencing this issue. First, your SD card may be locked. To fix this, remove the card and make sure that the lock switch is not pushed all the way down into the lock position. Second, your SD card may not be supported by the device. To fix this, you can either purchase a card with a smaller GB storage or upgrade the software on your tablet. Third, your SD card could be damaged. If this is the case, the card will not be recognized by the device, making your apps inaccessible.