An internet connection is not required for charging. If Time of Use (TOU) is set and the JuiceBox goes offline, it will continue to charge the car according to the preset schedule. To override the schedule in the offline mode, you will need to reset the JuiceBox by powering it off, waiting 15-20 seconds, and powering it back on. The unit will offer a charge immediately when plugged into the car.
Also, if you have adjusted the amperage limit via dashboard/app before, the unit will remember that last wire rating (amperage setting) in its memory until it is changed again online.