yeah, you might be right. I got mine several years ago, didn't remember that. The only thing I can think of is to try another adaptor. If you search on this forum, there are more people with the same issue. You might find a solution there. Good luck.
Have you tried putting the cable in a different USB port? Or taking it out and putting it back in? If I leave my cable in the same port for months, sometimes that happens to me. You also might want to try turning the watch off and on again if you haven't done that.
