First, please check your network connection.
Second, please check if your SD card is full. All scanners sold before November 2014 are supplied with 4GB SD card. As Foxwell keep issuing new updates to improve the products, there might not be enough space for the 4GB SD card of NT644. Our suggestion is to replace it with a 8GB SD card. Alternatively, you may delete some of the vehicle software that you are not in need to make room for future updates. Please remember it's always suggested to delete and update software via the update client FoxScanner.