Your Identity Provider appears to be sending an error in the SAML Response. Please log in to the Joomla administrator dashboard and go to the SAML plugin to see what the problem is. Click Test Configuration in the Service Provider tab and look at the IDP’s issue. If it’s an ADFS responder, launch the event viewer and look for the error. You may find the opening event viewer in ADFS by searching for it in the Start menu.