Try the instructions again: https://www.digitsole.com/wp-content/uploads/2018/08/Warm_Series_User_manual.pdf Activate location. Bluetooth and WLAN. If that doesn't help, you may have a defective product. :C

According to the manufacturer's page, the battery should last from 2.5 hours to 8 hours. I assume then around 2.5 hours at maximum strength. https://digitsole.com/shop/heated-insoles-warm-series/