Thank you for taking your time on submitting this question.
From the looks of this setup, the expresion looks to be valid.
Please visit the Okta Admin Dashboard, open you app and click on that application sign-on tab.
On the Application username format, select "Custom" and select the "Custom expression" url.
This will permit you to try and preview the mapping based on the examples you provided.
If you believe further assistance is required, please log a support ticket so that we can further investigate the issue.
Alex - Okta Support