If you are setting it to 72 by twirling the dial or pushing the up/down buttons, that's only temporary. At the next set point in the Nest's schedule, it will revert to following the schedule rather than your temporary override. (Even if you didn't set up a schedule, there may be a default one in there.)
First, make sure you have Home/Away Assist and/or presence sensing turned off. That "smart" feature can override your schedule.
We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.