Conflicting Errors with Google Cloud App Engine: App Already Exists But Can't Describe It

I'm running into a confusing issue with Google Cloud's App Engine and could use some help.

I'm stuck because the system is telling me both that an App Engine app exists and doesn't exist in my project.

Here's what I've checked so far:

Tried to create one using the UI with default config, got "Error while initializing App Engine" message.
Verified the project configuration.
Tried deploying a hello-world Node.js app with zero extra setup on app.yaml.
Considered region mismatch.

Outputs:

$> gcloud app create --project=xxxx-000000 --region=us-central

You are creating an app for project [xxxx-000000].
WARNING: Creating an App Engine application for a project is irreversible and the region
cannot be changed. More information about regions is at
https://cloud.google.com/appengine/docs/locations.
ERROR: (gcloud.app.create) The project [xxxx-000000] already contains an App Engine application. You can deploy your application using 'gcloud app deploy'.

$> gcloud app describe

ERROR: (gcloud.app.describe) The current Google Cloud project [xxxx-000000] does not contain an App Engine application. Use 'gcloud app create' to initialize an App Engine application within the project

Solution

This issue might be related to the region setup of your Datastore or Firestore, if you're using either of these services. A mismatch can occur between the region where Datastore or Firestore resides and the region where App Engine is attempted to be created, especially if Datastore is created first and then attempts to create an App Engine app in a different region.This is a known behaviour which may occur.

Solution - Delete the existing Datastore/Firestore default database and reattempt App Engine app creation in specific region

As stated here, you might be facing the same issue

The error you encountered during the initialization of App Engine could be due to a region mismatch between your Firestore database and the region specified when creating the App Engine instance.

If you already have a Firestore database deployed in region region-a Then the app engine in the same project must be deployed in the same region region-a.