To solve this issue: 

Put the Earbuds inside the charging case

Using the C-Type usb cable reveived with the product, connect the Charging case with the charging cable to the USB port on the laptop/computer

Make sure that your PC/laptop is turned ON and not in sleep / hibernate mode

If it still doesn't work try with a different USB port on your laptop/computer just to be sure whether an issue exists with your USB port

Note: Kindly ensure to remove Cellophane Paper from Earbuds as this may lead to several issues with Earbuds