Yup. My 64gb Ultra micro SD card is dead as well. Write only. Old content can be read but deleting/formatting does nothing. Really disappointed to have 2 Sandisk products fail on me this year.Also, trying to RMA a storage product with personal files on it is a no-go for me. Ridiculous situation that I will avoid by not purchasing a Sandisk card for a replacement.
contact sandisk support. they have a process for returning cards with sensitive data on them. they will be happy to work it out for you.