Heroku: Your account has reached its concurrent build limit

I'm trying to deploy my app to heroku, currently using the free tier. Over the past 5 days I've been redeploying the app as I made changes. I went overzealous with the deploys and now my app is up to version 35 on heroku under the "activity" tab.

Now the error message in the title prevents me from deploying my app. Google search didn't return a thing. If I have reached the deployment limit how do I delete/free up my concurrent build space?

For my case, heroku restart worked.

We can cancel the current build. Or any ongoing build using below

heroku builds:cancel

You can check the list of builds using

heroku builds

Or you can cancel any build using build hash from the above result list.

In case builds command not working, you need to install it using

heroku plugins:install heroku-builds

I had to try two of these answers back-to-back. Individually, they didn't work for me.

I needed to install heroku-builds with

heroku plugins:install heroku-builds

Then cancel the ongoing build with

heroku builds:cancel

And finally did a heroku restart.