Outlook Client Configuration Error Object reference not set to an instance of an object AddHiddenControlsForCustomControl Dynamics 365 On Premise

When attempting to configure an organization for the CRM Outlook Client 2016 the configuration fails with the following error:

07:49:27| Error| Exception : Object reference not set to an instance of an object. at Microsoft.Crm.Application.FormDescriptor.AddHiddenControlsForCustomControl(XmlNode formNode, EntityMetadata entityMetadata)
at Microsoft.Crm.Application.FormDescriptor.Initialize(EntityMetadata entityMetadata, XmlNode formXml, Guid formId, FormType formType)
at Microsoft.Crm.Application.FormDescriptor..ctor(EntityMetadata entityMetadata, XmlNode formXml, Guid formId, FormType formType, Boolean isUserForm, Boolean isActive, IOrganizationContext context)
at Microsoft.Crm.Application.Forms.FormDescriptorLoader.LoadCacheData(FormDescriptorCacheKey key, IOrganizationContext context)
at Microsoft.Crm.Caching.CrmMultiOrgCacheBase`2.CreateEntry(TKey key, IOrganizationContext context)
at Microsoft.Crm.Caching.CrmMultiOrgCacheBase`2.LookupEntry(TKey key, IOrganizationContext context)
at Microsoft.Crm.Application.Outlook.Config.OutlookConfigurator.InitializeMapiStoreForFirstTime()
at Microsoft.Crm.Application.Outlook.Config.OutlookConfigurator.Configure(IProgressEventHandler progressEventHandler)
at Microsoft.Crm.Application.Outlook.Config.ConfigEngine.Configure(Object stateInfo)

Not sure where to look except for maybe a Form which might be configured in a way that it is having problems in XML format. Any help is appreciated.  Thanks.