I'm an exercise watch novice and bought the 735xt because I want data from the pool but lately it hasn't been uploading.

The watch functions well while I'm am swimming, recording distance in my 25yd pool and time. At the end of the workout, I scroll down to "save" and hit the play/pause button. It then either flashes the blank "GARMIN" screen or resets to 0. Nothing shows up on Strava when I then sync.

Bike and swim workouts are fine.

Anyone know why this is happening?