If the LED blinks (3 times per second), the autoloader was old or incorrect. You must find a newer 10.3.3 build.

Reliable sources for the 10.3.3.2163 (T-Mobile) or 10.3.3.2205 (General) autoloader files include:

Before downloading the autoloader, make sure you have the following:

Failure to prepare can result in a soft brick. Follow these steps: