I love mine too. It helps me push further in my workouts, running etc.
I've had it 10 days now and my results are in the pictures below.
I've synced mine the day after and haven't had any issues, it seems to remember. Your situation sounds odd. Did you check that your Nike app was on the right day? View attachment 337222
View attachment 337224
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Yeah, I checked the activity and it just shows up as 0 for my 2nd day. I will wait until tonight and see what happens. When I sync it w/ my phone throughout the day, I see it working as the fuel points move on my phone. Hopefully I won't lose all my data again tonight or I'm going to return this.