SanDisk iXpand 64GB Flash Drive for iPhone and iPad saying it's full

Hi there, first post! Having trouble with my SanDisk iXpand 64GB Flash Drive for iPhone and iPad. Am trying to copy files from iPhone SE to the flash drive. The drive is saying ‘64 GB used of 64 GB’ - so it’s saying it’s full. If I try and save a file I get a message saying ‘iExpand drive is full - operation could not be completed’ Yet when I go to VIew Files on the drive there are no files there. So what’s taking up the 64GB? If I have used it why can’t I see the files? Incidentally I’ve used 54GB of 64GB of my phone storage if that has any bearing on this.

what is the size of the file you are trying to transfer? connect the ixpand to the computer and verify what file system is on the ixpand. If it is FAT32 you cannot transfer files larger than 4GB. in order to do that you would need to reformat the drive in exFAT. 

Also if you have a mac and have deleted files using the mac you need to empty the trash or the space does not free up. if you have done that you will need to use disk utility to format the drive. use MS DOS file type or exfat for the file system and set it up an MBR partition. 

I’m having this issue too. At first I was trying to clear some space using the iXpand app, but then it took a long time than usual & I had to force close it. Later I clear some space in it using a windows pc, but the app still detected it as full when connected.