Why can't I add my Heroku External Objects to my Salesforce org?
You've enabled External Objects in Heroku Connect, but you can't select OData as a Type in the New External Data Source page. You may only see a choice that says Simple URL.
In order to use Heroku External Objects in your Salesforce org, you'll need to make sure you have a license for Salesforce Connect. You may need to contact Salesforce support to add the license to your current agreement.