YOU NEED TO USE ATF 10.41 or HIGHER VERSION IN ORDER TO FLASH LUMIA 1520.
GET ATF 10.41 via ATF AUTO UPDATE SERVER.



ATF First In The World Lumia 1520 WinPhone 8 Full Flashing!
Also check out other Lumia WinPhone 8 Phones Flashed by ATF:

ATF First In The World Lumia 520 WinPhone 8 Full Flashing!
ATF First In The World Lumia 620 WinPhone 8 Full Flashing!
ATF First In The World Lumia 625 WinPhone 8 Full Flashing!
ATF First In The World Lumia 720 WinPhone 8 Full Flashing!
ATF First In The World Lumia 810 WinPhone 8 Full Flashing!
ATF First In The World Lumia 820 WinPhone 8 Full Flashing!
ATF First In The World Lumia 822 WinPhone 8 Full Flashing!
ATF First In The World Lumia 920 WinPhone 8 Full Flashing!
ATF First In The World Lumia 925 WinPhone 8 Full Flashing!
ATF First In The World Lumia 928 WinPhone 8 Full Flashing!
ATF First In The World Lumia 1020 (Nokia 909) WinPhone 8 Full Flashing!
ATF First In The World Lumia 1520 WinPhone 8 Full Flashing!

You Can Download Flash Files Here:
Nokia Product Code Listing for Care Suite Download - (Nokia 925T Added)


Another Lumia WinPhone 8 Flashed Successfully with ATF...
Here is the Screenshot: