Cant progress story on jakku [Solved]

So I had same problem nothing worked to fix it but nifty way to get around.

1: I changed gameplay to easiest ( explorer) to make a bit more manageable 

2: change your Loadout gun to the high powered TL-50 

3: fire away- destroy the little Walker things and there's a couple of loads of troopers that come but once they are done you are free to fire on the big AT- AT  - they don't actually come closer so U need to go as close as U can and fire blast up high so it hits them, if U have grenades throw them too. It takes a while but U can destroy them this way. :P 

Happy hunting.