This is probably an issue because of the fact that your default IdP is using the Contractor user source. What happens when you switch the user source for the IdP to the Customer user source?
There is a Customer IdP that uses the Customer user source
In the gateway security settings the System Identity Provider is set to Customer.
What I find really odd is that the Administrator role is ONLY defined in the Contractor user source and the Contractor user source is never explicitly called out anyway.
Could you post what screen or error message you are seeing which leads you to this conclusion? This may help diagnose the issue.
Have you tried a Test Login against the Customer IdP to confirm whether your user who should have IGN_Administrator role actually has the role show up in the security level tree in the test login results page?