Raise AD Forest Functional Level
In PowerShell type $CurrentForest = Get-ADForest Set-ADForestMode -Identity $CurrentForest -Server $CurrentForest.SchemaMaster -ForestMode Windows2008R2Forest
In PowerShell type $CurrentForest = Get-ADForest Set-ADForestMode -Identity $CurrentForest -Server $CurrentForest.SchemaMaster -ForestMode Windows2008R2Forest