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
Official Inventory】Fitbit Charge 3 Smart Sports Watch - One year warranty | Lazada
For Fitbit Charge 3 4 Classic Silicone Replacement Band Watch Strap Sports band | eBay
Fitbit Charge 3 SE Fitness Activity Tracker - Lavender Woven / Graphite White Silicone – Style Vision Computer Store