What is the reason behind error h14 "No web processes running" and Application error?

I made this project and deployed it on Heroku successfully and it was working, I checked it again two months and it was working properly, but today when I tried to open the website link it says Application error.

Logs are as follows:

2022-12-06T08:17:30.897980+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/" host=limitless-shelf-83830.herokuapp.com request_id=d0c862ec-c21d-4e94-94e5-f6fed3d71af6 fwd="103.141.116.193" dyno= connect= service= status=503 bytes= protocol=https
2022-12-06T08:17:31.345120+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/favicon.ico" host=limitless-shelf-83830.herokuapp.com request_id=a98c5850-0aa3-413d-94d9-4480a218ec3d fwd="103.141.116.193" dyno= connect= service= status=503 bytes= protocol=https

Is this issue from my side or heroku servers are down? What is the cause of this error and what are possible solutions?

I tried running

heroku ps:scale web=1

but it had no use.

Edit: I found the issue, Heroku has stopped offering free plans from 28th Nov 2022, and I deployed it free server.

As you mentioned, Heroku no longer provides free dyno plans.

Although if you have previously deployed apps, you can still access them after subscribing to one of their plans. If you are still experiencing an H14 error, try to reconfigure your dyno. Just change your dyno type to the subscribed plan and make sure you have toggle the selected dyno to the right in order to enable it.