I've tried reformatting as portable storage and internal storage and neither work, choosing portable storage shows no errors it just doesn't do anything while internal storage errors.
I've tried taking out the card and plugging it into my computer to reformat but Windows doesn't pick it up at all (including the SDFormatter tool) and GParted gives the following error when trying to change anything:
Input/output error during write on /dev/mmcblk0
Error fsyncing/closing /dev/mmcblk0: Input/output error
Trying to reformat it using the Disks tool in Mint gives me this error:
Error synchronizing after initial wipe: Timed out waiting for object(udisks-error-quark,0)
The parted command line tool gives similar errors.
I've been tearing my hair out all day over this, I can't seem to find any way to bring the SD card back. This is actually the second card this has happened to, I ended up throwing away the first one and then I've gone and done it again.
I've had a look at http://nelenkov.blogspot.co.uk/2015/06/decrypting-android-m-adopted-storage.html, but as I've flashed a new ROM the key is gone?
Any help is appreciated!