SP Initiated SAML Authentication stops at Webtop page

Ah, I had wondered how it matched up the incoming SAML request with the SAML resources that have been configured.

The 3rd party has confirmed what the ACS URL should be, the URL in the original metadata was incorrect. I've manually corrected it under Access -> Federation -> SAML Identity Provider -> External SP Connectors, and cleared off am my SAML sessions, but it's still getting the same result. Should the change have taken effect immediately?