Unknown error from provider - idp initiated SSO with auth0 as SP


I’m trying to set up my auth0 app as a service provider for IdP-initiated SSO. I’ve created my enterprise SAML connection and configured all that according to all of the auth0 docs I could find. When I go to the IdP and launch the portal to my app, it loads for a second then displays a blank screen. In my auth0 logs, I can see a failed_login error with message unknown error from provider. The body of this error messages contains a saml payload that contains all of the information I expected, and indicates a SAML protocol success.

This error message / type gives me very little to go on, has anyone seen this before?

Thank you!

I can also confirm that I have no rules running, which seems to be a common source of this error.