I have put it on both the FR935 and he Fenix 5X without issues I have seen other posts of users having the same just don’t remember what they did to solve it. Look in the Newfiles and RemoteSW folders and see if there are any files just hanging out.
Tried this on my F5. Activities sync up fairly quickly. Common metrics like Distances are not updated though. So, even though I did a 5AM 20K ride this morning, my watch still says 3.3k - my walk.