An internet connection is not required for charging. Even if the JuiceBox goes offline, it will continue to charge the car according to preset schedule. To override the schedule in the offline mode, you need to reset the JB by unplugging from power, waiting for 15-20 sec and plugging back in. Then the unit will offer a charge immediately when plugged into the car.
Besides, if you have adjusted the amperage limit via dashboard/app before, the unit will remember that last wire rating (amperage setting) in it's memory until it is changed again online.