This may be due to several reasons. Try using different power sources to check if the problem may be due to the USB port you are using or even the cable itself.
We recommend that you always use the cable supplied with the product. Several of our models have accessories to charge them (charging dock, base, etc.), so we recommend that you check the connection between the accessory and the wearable to make sure it is correctly made.
Our latest smartband models do not need a cable or accessory to charge them. Once the core of the wristband is removed, the USB connector is available for connection. Keep in mind that this connector is made of the charging pins, make sure you connect it correctly. Adjusts the position of the wristband core to the USB port. If it does not charge, try several USB ports. When the correct charging connection is made, the wristband will vibrate and display the battery charging process icon .
Also, check that there is no dirt in the charging contacts. If there is, you can clean the contacts easily with a clean, dry cloth.