I have had the 235 for about two weeks. Sometimes it stays connected just fine. Other days like today, I go into Controls on the watch and the blue tooth just says "Waiting to Connect". I have the app on my phone open and blue tooth is turned on there. Sometimes it seems to resolve itself by charging the watch. But that doesn't mean this issue is caused by a low battery. It shows that it has about two thirds of its battery left.
How do I know if it needs to be returned?