What SD card reader are you using to write the card ?
A 64GB Evo card is an SDXC card - this cannot be used in an older SD card reader/slot that is only SDHC compatible. Many older laptops and older SD card readers are only SDHC and therefore not SDXC compatible - so if the reader does not specifically say it is SDXC compatible this is your problem.
When I got a 64GB Samsung Evo card I had to buy a new USB SDXC compatible reader to be able to write to the card as neither the slot in my laptop nor the older USB reader I had was compatible.
You will see a drive that appears to be only 1MB and cannot be written to on an incompatible reader.
Cards between 2GB and 32GB are SDHC, sizes 64GB and above are SDXC.