Issue
I'm seeing an "Application error" page when accessing my app and/or H14 "No web processes running" errors in the app logs.
Resolution
Starting November 28th, 2022, free Heroku plans will no longer be available. To keep your apps running, you will need to upgrade to paid dynos and paid data plans - see How do I upgrade from Heroku's free tier and begin using paid resources?.
If you are seeing an "Application error" page when accessing your app and "No web processes running" in your application logs, you don't have any web dynos running. To fix this, subscribe to a paid dyno type and then run heroku ps:scale web=<desired # of dynos>:<dyno type> -a <app-name> from the CLI or adjust the slider in the Dashboard to your desired number of web dynos - see Manual Scaling.
If you already have web processes running (i.e. check by running heroku ps -a <app-name>) and are still seeing the "Application Error" page, you'll need to check your app logs (i.e. via heroku logs) for the source of the error - this often involves fixing your application code.
If your free database was deleted and you want to restore its data, contact Support. Provision a new Mini or Basic database on the app you want the database to be restored to and provide Support with the new attachment name.