Error when installing/connecting to Outlook Client for MS CRM 2015 (on-prem)

Having installed the Outlook Client I then try to connect to CRM on-prem and get the following error:

Excerpt from the log file is below - any ideas on how to resolve would be great - Thanks!!

Microsoft.Crm.Application.Outlook.Config.OutlookConfigurator.InitializeMapiStoreForFirstTime
16:32:27|  Error| Exception : context    at Microsoft.Crm.Metadata.MetadataCache.GetInstance(IOrganizationContext context)
   at Microsoft.Crm.Application.ControlDescriptor.get_Metadata()
   at Microsoft.Crm.Application.FormDescriptor.GetChildColumns()
   at Microsoft.Crm.Application.FormDescriptor.AddHiddenControls(EntityMetadata entityMetadata)
   at Microsoft.Crm.Application.FormDescriptor.InitializeObjectModel(XmlNode formNode, EntityMetadata entityMetadata, FormType formType)
   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.CrmSharedMultiOrgCache`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)
16:32:27|  Error| Exception : Value cannot be null.
Parameter name: context