Full Story is not replicating data to Azure SQL Dataware house

I am able to create the integration with Full story with invalid API key.
Why stitch doesn’t throw back any error about authentication/key? It is not replicating/syncing data from full story to Azure SQL Dataware house even when I provide a valid key as well.

Is there a handshake happening properly?

Fullstory is a community-developed and -supported Singer integration. Your best bet would be to either open an issue on the repo or contact the author on Singer Slack.