My Sync has seen two or three updates since I bought the Fusion. Note that the USB port has to work for you to do the updates, since you load them to a USB flash drive or device, and do the update through the USB port.
If you can get the USB port to work for a short while by resetting the fuse, maybe it will work long enough for you to get the update to take. I think they (SYNC) say it could take as much as 30 minutes with the key on, but your instructions might be different. Mine never took more than about 10 minutes.
Although it's been a while, I had some trouble with the online instructions for the update. I seem to recall that the steps didn't work exactly as detailed, and I think I may have written my own as I went through it. If you get to that point, send me a PM and I'll see if I still have them. (Not sure if our sound systems are identical)
Updating might also reset any bluetooth pairing you may have done, so you may have to start from scratch there if you use it.