Many issues encountered whilst using Heroku can be resolved by reading our documentation on Dev Center, or by searching with useful keywords on https://help.heroku.com.
For application issues, you will often find your logs will have the required information, allowing you to fix this quickly. You can view your logs by running the CLI command:
$ heroku logs --tail --app your_app_name
If you are seeing Heroku error codes (e.g., H10, H12, or R10) in your logs, you can read about why these happen, as well as suggested fixes on our Dev Center article: Heroku Error Codes
For HTTPS, TLS/SSL, Custom domains, and DNS issues, we have lots of information available to help you on Dev Center: