You may be unable to propagate changes after adding StoreFront Server to existing Server Group. The propagation fails with following event in Citrix Delivery Services event log:

Log Name:      Citrix Delivery Services
Source:        Citrix Configuration Replication Service
Date:          dd/mm/yyyy hr:min:sec AM/PM
Event ID:      1
Task Category: (2850)
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      Computername.domainnamel
Description:
An error occurred running the command: 'Install-DSFeatureClasses' 
The feature data is out of date
At C:\Program Files\Citrix\Receiver StoreFront\Services\ConfigurationReplicationService\Cmdlets\ConfigurationReplicationServiceModule.psm1:86 char:9
+         Install-DSFeatureClass "$($installPath)$($featurePackage)"
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The feature data is out of date

You may see following error in Install-DSFeatureClass (ResourcesCommon)_<date and timestamp>.log present on the StoreFront server you are trying to add:

Citrix.DeliveryServices.Framework.FileBased.Exceptions.StaleDataException: The feature data is out of date
   at Citrix.DeliveryServices.Framework.FileBased.Abstractions.FileBasedFrameworkControllerBase.Save()
   at Citrix.DeliveryServices.Framework.Abstractions.FrameworkControllerBase.AddClass(FeatureClass featureClass)
   at Citrix.DeliveryServices.Framework.Abstractions.FrameworkControllerBase.InstallFeatureClassFromFile(String packageFilePath)
   at Citrix.DeliveryServices.Framework.Administration.Commands.Feature.InstallDSFeatureClass.ProcessRecord()
DSFeatureClass: Error The feature data is out of date

The log is located at <Drive letter:\> Program Files\Citrix\Receiver StoreFront\Admin\logs\Install-DSFeatureClass

1. Go to folder path <Drive letter:\> Program Files\Citrix\Receiver StoreFront\Features\ResourcesCommon on StoreFront server you are trying to add
2. Move all the directories within ResourcesCommon to an alternate location 
3. Propagate changes from StoreFront console.

Problem Cause