I ask about the card because I've been looking recently at different ways to access data from drives which are inaccessible because of corrupt files or file systems.
An SD card is simply another type of flash drive, and I've been doing some testing by writing new Partition Boot Records to a 32MB SD card which came with my camera, and so far it's still working as it should.
After doing a little reading, I believe the error you experience could possibly be caused by a single corrupt file or a corruption of the bootsector/partition table. This may be the case because you haven't physically deleted all the files or formatted the SD card.
I emphasise "possibly" because there's no way to know exactly the state of the card, and I don't want to raise false hopes.
I'm a long way from being an expert in this, so I've been going down the road of finding a way to make a back up of the drive involved first, before looking at ways to carry out a repair to it, so if you want to give this a try I'm happy to guide you through it.
The first thing I would like to know is do you have a card reader on your laptop or desktop, and have you tried plugging the card into it as opposed to having your phone connected via cable?
If so does Windows recognize it?