In two visits this week, no cell service for NAV or Tesla App at Topaz Lodge (Misnamed Gardnerville by Tesla).
Your smart phone can connect, but not the car, so NAV can't find the route and distance to your next stop and the Tesla App cannot tell you progress of charging. If you have already entered the next stop into NAV, the charging window can notify you on the main screen when you have sufficient charge to get there, but not via Tesla App.
You will do best to input your next destination before you leave the towns of Minden/Gardnerville (30 miles north of the SC), if headed south, or before leaving Mammoth Lakes or possibly Lee Vining, if headed north. If you wait until you arrive at Topaz Lodge, you will have to use google maps on your smart phone to get distance to the next supercharger of your destination and calculate required SOC by yourself.