Could you enter in Disk Management and check if the SD card is listed there? Does it have a file format and a drive letter? If there is no drive letter assigned, try using the Diskpart command from Command Prompt to assign one.
It should look like this:
Select volume n
Assign letter =L (or whatever letter you like and is not in use)
I strongly recommend you to check the SD card on another PC or on some other device.
Hope this helps