Issues with SD Card "Reinsert SD Card" for Internal Storage (Adoptable Storage) Android 6.0 (Marshmallow)
I guess it's either sd card dead or sd card slot faulty. However there is way to decrypt adopted sd card but if you factory reset device and wipe key you are screwed here is how to decrypt 
Btw try to put other sd card in your phone and see if phone is recognize it.