SharePoint SPFx extensions - Feature not working

Today I created a new dev tenant and I'm running into some issues when I go through these steps:

https://dev.office.com/sharepoint/docs/spfx/extensions/get-started/serving-your-extension-from-sharepoint

The feature "Application Extension - Deployment of custom action" does get deployed as the app is added however the custom action doesn't kick in when I load my lists.

When I deactivate the feature and then reactivate the feature things are kicking in as in my console I see:

Initialized ClientSideExtensionHelper

Defined clientSidePlaceholders: DialogContainer,PageHeader,PageFooter

Client-side host application loaded on SPO app

the footer and header however do not appear.

I'm not sure if I'm hitting one or two issues here. Has anyone else seen the features not activating properly on deployment?