Most probably, you haven't downloaded the correct driver for your operating system. To install the correct driver, use the link posted below and download the driver available for your operating system. I recommend choosing the latest one, since it has bug-fixes already incorporated.
TP-Link Support page for your product: http://www.tp-link.com/en/download/TL-WN727N_V3.html
Note: Choose the product version using the drop-down menu, and then download the drivers.