The following NullReferenceException is shown when you run the Test-FederationTrust cmdlet in Microsoft Exchange Server 2019 or Exchange Server 2016. This issue occurs when a new certificate for the federation trust is enabled, and the previous certificate has expired.
WARNING: An unexpected error has occurred and a Watson dump is being generated: Object reference not set to an instanceof an object.Object reference not set to an instance of an object.+ CategoryInfo : NotSpecified: (:) [Test-FederationTrust], NullReferenceException+ FullyQualifiedErrorId : System.NullReferenceException,Microsoft.Exchange.Management.SystemConfigurationTasks.TestFederationTrust
This issue occurs because a thumbprint property is still printed if null is assigned to orgPrevPrivCertificate when calling this.GetOrganizationCertificate in this situation.
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 7 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.For Exchange Server 2016, install the Cumulative Update 18 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.