You can’t leave a voicemail until the Skype for Business Front-End service gets restarted in a Microsoft Skype for Business Server 2015 environment.
In addition, the following events are logged on the Skype for Business Server 2015, Front End server:
Log Name: Lync Server
Source: LS Exchange Unified Messaging Routing
Date: DATE/TIME
Event ID: 44005
Task Category: LS Exchange Unified Messaging Routing
Level: Error
Keywords: Classic
User: N/A
Computer: SERVER
Description:
Exception: System.DirectoryServices.ActiveDirectory.ActiveDirectoryServerDownException: The RPC server is unavailable.
Name: "server.domain.com"
at System.DirectoryServices.ActiveDirectory.Forest.GetTrustsHelper(String targetForestName)
at Microsoft.Rtc.Internal.ExumDialPlanData.GetTrustedForests()
at Microsoft.Rtc.Internal.ExumDialPlanData.RefreshDomainDictionary()
Log Name: Lync Server
Source: LS Exchange Unified Messaging Routing
Date: DATE/TIME
Event ID: 44005
Task Category: LS Exchange Unified Messaging Routing
Level: Error
Keywords: Classic
User: N/A
Computer: SERVER
Description:
Exception: System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.Rtc.Internal.Domain.GetHashCode()
at System.Collections.Generic.ObjectEqualityComparer`1.GetHashCode(T obj)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at Microsoft.Rtc.Internal.ExumDialPlanData.RefreshDomainDictionary()
at Microsoft.Rtc.Internal.ExumDialPlanData.TimerElapsedEventHandler(Object sender, ElapsedEventArgs args)
Log Name: Lync Server
Source: LS Exchange Unified Messaging Routing
Date: DATE/TIME
Event ID: 44008
Task Category: LS Exchange Unified Messaging Routing
Level: Error
Keywords: Classic
User: N/A
Computer: SERVER
Description:
Dial Plan Unknown
Dialplan [DIALPLAN.domain.com] is not recognized by routing application
Cause: Dial plan does not exist, or Microsoft Skype for Business 2015 does not have permission to read the relevant Active Directory objects.