If you’ve received a Director Penalty Notice, don’t ignore it. The 21-day clock...

https://wiki-global.win/index.php/What_should_I_do_first_if_I_think_the_ATO_is_about_to_issue_a_DPN%3F

If you’ve received a Director Penalty Notice, don’t ignore it. The 21-day clock starts from the issue date, not when you open the letter