Heroku Review Apps not deploying at all - github

Question

I'm trying to automatically create review apps as part of my pipeline and testing procedure when pull requests are created on the corresponding GitHub repository. When the PR is created, it appears as a review app, but doesn't actually get created.
In the DevTools console, a 404 error is there about the review-app-config. I'm not sure if this is directly related, as I've successfully created a review app on a different pipeline (with a different owner) with the same error.
This 404 error changes between the file not being available at all, or that it's returning an error. When it's the latter, the file contains the following:
{"id":"missing_version","error":"Please specify a version along with Heroku's API MIME type. For example, `Accept: application/vnd.heroku+json; version=3`.\n"}
I'm creating and managing all of the apps/pipelines with the GUI on dashboard.heroku.com. The version accept header appears to be needed for the Heroku API but I've no idea how to implement it. Any help would be greatly appreciated!

Answer 1

Firstly check that your app.json file is valid json. If it isn't then that will cause the deployment to fall over.
Secondly check if you have any scripts in the app.json key. If you have any here and they are incorrect then this will also cause it to hand and fall over with no warning displayed.
{
"name": "App name",
"scripts": {
"deploy": "command that won't work!!"
},
...
}
You many not need any scripts in here so it can also be empty!
{
"name": "App name",
"scripts": {},
...
}