The specs of the Prime 6 says it can support a 64Gb micro SD card. I bought a legitimate Samsung card and copied music files to it in my computer. These files were readable by the computer, so the card appeared to work properly. But the phone did not recognise the card, and did not offer the option to mount the card, but when the card was removed it gave the message, 'card removed, insert new card'.
As mentioned in other posts here on the forum the problem is that the card has to be formatted to FAT32. This option isn't available in the phone, and Windows 7 can't format a FAT32 drive larger than 32Gb. I found a mention on another forum of a small third party program to do this. I don't know what the forum rules here are regarding links to commercial sites, so if This Link disappears google Ridgecrop Consultants and their page with 'Fat 32 Formatter'. It's free to download but you can donate via paypal (I have no connection to them.) It's simple to use, one click to format your micro SD card.
After formatting, the 64Gb card works fine in my Smart Prime 6.
You can apparently also format cards in certain phones. And if your problem isn't sorted by this route, you might need to check that your card works.
Vodafone, it would have been good to have had some warning, or maybe even a fix in updates?
