Exchange Installation error 5506 is caused by the 3rd party certificates. To resolve this always change to the Microsoft cert before beginning the upgrading to the next CU.
IIS > Bindings > SSL Certificate > Microsoft Exchange
The error returned was 5506. at Microsoft.Exchange.Configuration.Tasks.Task.ThrowError (Exception exception, ErrorCategory errorCategory, Object target, String helpUrl) at Microsoft.Exchange.Configuration.Tasks.Task.WriteError (Exception exception, ErrorCategory category, Object target) at Microsoft.Exchange.Management.SystemConfigurationTasks.InstallExchangeCertificate.EnableForServices (X509Certificate2 cert, AllowedServices services) a