Introduction

On an existing Terraform Enterprise Global GitHub App an additional GitHub Account is needed.

Problem

When adding an additional GitHub Account to an existing Terraform Enterprise Global GitHb App via the Terraform Enterprise UI, you get a:
Failed to install GitHub App: The response from the provider is missing these required response params: installation_id error.

Error example shown to the bottom right:

Cause

A probable cause is that the logged in Github user attempting to add the GitHub Account to the Terraform Enterprise Global GitHub App is not an administrator of the GitHub Organization or does not have the permission to install GitHub apps to the specific GitHub Organization.

The user lacking permissions sees a Request button on the GitHub pop-up:

A user with sufficient GitHub permissions sees an Install button:

Solution

If you use the Request button the GitHub Organization administrator will receive a notification for the Integration Installation Request.
The GitHub Organization administrator should attempt to add the GitHub Account or a GitHub user with permission to install GitHub apps to the specific GitHub Organization. . 

Outcome

The Terraform Enterprise Global GitHub app should be installed to the additional GitHub Account/Organization.