take it out and if you have another phone it can go in check to make sure for some reason its not now corrupt. if not then the only trick i have done is with it out of the phone run it for a little bit. restart it. then try putting it back in. if you take it into a repair store theyre just going to tell you, you need to reformat the sd card. does it not read it or does it say its corrupt?
The phone is unable to read the SD card, had this happen to my device also although it wasn't in relationship to the update. I put a new SD card in and it worked fine. I was able to get my computer to read the original card through a card reader, hopefully you can also. You may also be able to transfer the files to your computer and then format to see if it will detect it again.