Error - Could not find relationship in CRM 2016

Mar 17 at 2:54 PM
I am attempting to update all child records in an 1:N relationship using AG Utilities Distribute One to Many plug in.

It is run from a workflow on the parent entity. It calls a CHILD workflow on the child entity. However, I'm getting this error:

Unhandled Exception: Microsoft.Xrm.Sdk.InvalidPluginExecutionException: Could not find relationship
Server stack trace:
at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

Exception rethrown at [0]:
at Microsoft.Crm.Sandbox.SandboxOrganizationService.Execute(String operation, Byte[] serializedRequest)
at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)
at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg)

Exception rethrown at [1]:
at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at Microsoft.Crm.Sandbox.ISandboxOrganizationService.Execute(String operation, Byte[] serializedRequest)
at Microsoft.Crm.Sandbox.SandboxOrganizationServiceWrapper.ExecuteInternal(OrganizationRequest request)
at Gemina.CRM2015.WF.CrmDistributeWF.DistributeWFActivityOneToMany.GetRelationship(CodeActivityContext executionContext)
at Gemina.CRM2015.WF.CrmDistributeWF.DistributeWFActivityOneToMany.GatherKeys(CodeActivityContext executionContext)
at Gemina.CRM2015.WF.CrmDistributeWF.DistributeWFActivity.Distribute(CodeActivityContext executionContext)
at Gemina.CRM2015.WF.CrmDistributeWF.DistributeWFActivity.ExecuteBody(CodeActivityContext executionContext)
at Gemina.CRM2015.WF.CodeActivityBase.Execute(CodeActivityContext context)

Any help is appreciated!
May 23 at 2:59 PM
I have the problem with the workflow too. Is it compatible with Dynamics 365?