A little late, but if anyone else has this issue, open up the controller and check for loose /disconnected wires. My x12 started having this issue last night and took a lot of messing with the controller to get it to sync. I realized it was a controller based issue because as soon as I turned the controller on, it would act as though it instantly synced (no flashing lights). This morning I couldn't get it to sync at all. After opening the controller, I found a loose wire. I initially thought this wouldn't fix the issue considering it was part of the elevation /spin control. Resoldered the wire and voila! Problem solved! Far from the best drone but for the price, I have no complaints and I'm actually impressed with its performance in comparison with other drones in this price range.