I know this isn't much help now.. but.. maybe it is. Do you still have a backup of your FTM tree that was syncing properly? Ancestry likes to tell us to re-sync the online tree because to them .. well, I don't know why. The real solution if sync MUST be broken is to UPLOAD a new tree from Family tree maker. Best first to re-name your old tree online and then you can name the new tree with the same name that you had before. You WILL have to re-invite people to your tree. This way you do not lose all the hard work you put in to Family Tree Maker.