To properly charge your Woojer Vest 3, please make sure to utilize the provided Power Delivery charger, and make sure it is plugged into the USB-C port located on the back of your Vest 3.
The LED should be blinking red while charging and blinking green when fully charged instead of solid red and solid green as reflected in the manual.
You can refer to the following image to see where your Vest's USB-C charging port is located:
