My son is having exactly this same issue. His watch is syncing with Connect IOS just fine, but all of his challenges are showing 0 steps with a note that "steps have not been sync'd", along with a button to "sync now", which does nothing when you tap on it. It makes no sense, I cannot figure out why it isn't working. I, too, have uninstalled Connect on his phone and reinstalled it, which made no difference.
