The http://www.w3.org/2000/09/xmldsig#rsa-sha1 algorithm has been removed as of Java 17.
More details:
https://github.com/FusionAuth/fusionauth-site/issues/1202
https://fusionauth.io/docs/v1/tech/release-notes#version-1-32-0
This error means you are using an SAML v2 IdP that is signing their Authn response with RSA-SHA1. The best way to solve this is to change the signing configuration if you have access to that, or request the owner of that IdP sign their response using a more secure, modern algorithm.