Hello,
You haven't shared any error message ( error which is throwing from IDP / Gluu Server ). Anyway, you can check further SAML issues in `/opt/shibboleth-idp/logs/idp-process.log` https://gluu.org/docs/gluu-server/4.5/operation/logs/#adjust-shibboleth-log-level
Also, a note... Gluu 4 is behind paywall now. You need a subscription to get support for Gluu 4.
On the other hand, [Linux Janssen Project](https://docs.jans.io/v1.1.2/) is free to use and you can get community support there in [forum](https://github.com/JanssenProject/jans/discussions).