The Canvas error "vantage.sagepub.com sent an invalid response" indicates an incomplete tool configuration.

Once you create the developer key in your Canvas environment, you need to send your Canvas URL and the LTI Client ID that is generated when you create the tool setup. The LTI Client ID is a long series of numbers that is tied to the Developer Key once it's created.

Your Sage Technical Implementation Specialist uses your Canvas URL and the LTI Client ID to complete the tool configuration on the Sage side.