SLO Error out of the blue

We have SSO and SLO implemented on a site that is running .NET Framework 4.6.2 and ComponentSpace 2.8.8, in an ASP.NET MVC web application.

The SSO/SLO functions normally in Production, but in the UAT environment, we have recently noticed that SLO has stopped working. This work coincided with changes being prepared for deployment, so we rolled back to the version that is also in production and experienced the same problem. I talked to the IdP team and they have not updated the configuration (IdP is Okta). But I wonder if there are any Windows Server updates or other security changes on the server-level that would cause an outage like this?

I forgot to add the error message:

ComponentSpace.SAML2.Exceptions.SAMLProtocolException: A logout response was unexpectedly received.
at ComponentSpace.SAML2.AbstractSAMLProvider.ProcessLogoutResponse(HttpRequestBase httpRequest, XmlElement logoutResponseElement, String signatureAlgorithm, String signature) in C:\Sandboxes\ComponentSpace\SAMLv20\Library\AbstractSAMLProvider.cs:line 666
at ComponentSpace.SAML2.InternalSAMLServiceProvider.ReceiveSLO(HttpRequestBase httpRequest, Boolean& isRequest, String& logoutReason, String& partnerIdP, String& relayState) in C:\Sandboxes\ComponentSpace\SAMLv20\Library\InternalSAMLServiceProvider.cs:line 1175
at Application.UI.Controllers.SAMLController.SLO() in S:\Agent002_work\2614\s\Application.UI\Controllers\SAMLController.cs

I’m not aware of any Windows Server updates or security changes that would cause issues with SLO.

Please note that v2.8.8 is eight years old and no longer supported. Upgrading to the latest version and staying current is highly recommended.