Hi,
We get the same error when trying to link on premises sharepoint 2013 with on premises CRM 2016.
The Web Service plug-in failed in OrganizationId: 521f0ebd-3e4a-4552-8252-79d5b04f9f5c; SdkMessageProcessingStepId: e0bdf6d6-0b83-4aba-838f-f7b4a31afd72; EntityName: sharepointdocument; Stage: 30; MessageName: ValidateSharePointSite; AssemblyName: Microsoft.Crm.Extensibility.InternalOperationPlugin, Microsoft.Crm.ObjectModel, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35; ClassName: Microsoft.Crm.Extensibility.InternalOperationPlugin; Exception: Unhandled Exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Web.Services.Protocols.LogicalMethodInfo.Invoke(Object target, Object[] values)
at Microsoft.Crm.Extensibility.InternalOperationPlugin.Execute(IServiceProvider serviceProvider)
at Microsoft.Crm.Extensibility.V5PluginProxyStep.ExecuteInternal(PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
Inner Exception: System.Xml.XmlException: An error occurred while parsing EntityName. Line 7, position 171.
at System.Xml.XmlTextReaderImpl.Throw(Exception e)
at System.Xml.XmlTextReaderImpl.HandleEntityReference(Boolean isInAttributeValue, EntityExpandType expandType, Int32& charRefEndPos)
at System.Xml.XmlTextReaderImpl.ParseText(Int32& startPos, Int32& endPos, Int32& outOrChars)
at System.Xml.XmlTextReaderImpl.FinishPartialValue()
at System.Xml.XmlTextReaderImpl.get_Value()
at System.Xml.Linq.XContainer.ReadContentFrom(XmlReader r)
at System.Xml.Linq.XContainer.ReadContentFrom(XmlReader r, LoadOptions o)
at System.Xml.Linq.XElement.ReadElementFrom(XmlReader r, LoadOptions o)
at System.Xml.Linq.XElement.Load(XmlReader reader, LoadOptions options)
at System.Xml.Linq.XElement.Parse(String text, LoadOptions options)
at Microsoft.Crm.ObjectModel.SharePointProxyBase.ValidateSharePointSite(String[] siteUrls, String& validationLog)
.