I didn't have adequate permissions on my database user. Rather than raising an error Piwik just fails silently. The database user needed permissions to create the archive tables. Piwik simply fell over and failed to display the Ecommerce and Goals page.
CREATE privileges are tested during installation when Piwik creates the core tables.
We don't raise an error in the GUI because archiving may have been triggered by cron. You should have seen something in your error logs though.