Same here,
Originally the error was a HTTP 400 on /authorize with an entry on Auth0 logs:
The specified redirect_uri '<app_id>://<domain>/capacitor/<app_id>/callback' does not have a registered origin.
Then, and even thought the documentation says to only configure:
capacitor://localhost, http://localhost
I also added the callback url to the allowed origins
<app_id>://<domain>/capacitor/<app_id>/callback
Now the error is:
Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('<app_id>://') does not match the recipient window's origin