tl;dr: Heroku’s free plan is going away. Please update your services and make sure all your 3rd party libraries are up to date.
From their recent post:
Starting October 26, 2022, we will begin deleting inactive accounts and associated storage for accounts that have been inactive for over a year. Starting November 28, 2022, we plan to stop offering free product plans and plan to start shutting down free dynos and data services. We will be sending out a series of email communications to affected users.
Roughly 300 plugins use heroku services, many for free. If you are one of those free users, please make sure you make arrangements to either pay for the plan or replace your service. As of December 2022, if people report your plugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party breaks because of that shut-down, we will close your plugin until it’s corrected.
There’s always the probability you’re not going to want to (or be able to) migrate services. That’s okay too. If you want to close your plugin, you can do that yourself! I would recommend pushing a final version that warns people on day X this will stop working, if that’s your choice.
The one thing that’s really going to trip people up are those libraries though. A lot of 3rd party libraries make use of Heroku, and not all are going to update.
We’re going to do a sweep and let as many people know as we can, but we wanted this to be public since a lot of people miss emails and also if your plugin isn’t impacted but one you coordinate with is, well… you should know too 🙂