Sandisk Ultra 64gb MicroSD Wont format.

i have the same prob but on micro-sd card, i bought it from dealer and able to use it for 2 months. Unfortunately, it can’t be recognized either in SG 3, or Sony’s and it quite dissapointing. 

Do you know a way to make it workable/detectable again. I’ve tried via PC, and no response.

tq