Licenses purchased before the most recent migration in July of this year won’t renew. You’ll need to buy a new license and apply it with the
virtualmin change-license command.
Here’s one of the News announcements about the migration: Virtualmin.com migration - #2 by Joe
The good news is once you have a new license, you’ll be able to manage it completely without any assistance from us (i.e. you can upgrade/downgrade the size, cancel, renew, update card details, etc.) much more easily than the old site. The bad news is that I never figured out a reasonable way to migrate the old orders over (because the way Drupal Commerce treated subscriptions and the way WooCommerce Subscriptions does was just too different for me to sort out…things got ugly when I tried, so we punted and launched without the old orders coming across), though we did figure out how to get some of the billing info brought across.