My Charge 3 did this today. Warranty was up three weeks ago. Fitbit had every right to deny to replace it, but 10 minutes with tech support chat and they are shipping
What warranty does the Fitbit Charge 3 have? | iMore
Fitbit Charge 3 Fitness Activity Tracker Heart Rate Monitor more color | eBay
Amazon.com: FunBand for Fitbit Charge 3 /Charge 3 SE/Charge 4 Soft Silicone Sport Straps : Clothing, Shoes & Jewelry