Unexpected exception from plug-in (Execute)

Unexpected exception from plug-in (Execute): IBS.MSCRM.IBSConstruction.FetchXMLReturnConsProjectParticipant: System.IO.FileNotFoundException: Could not load file or assembly 'IBS.MSCRM.Core.Library, Version=1.0.0.0, Culture=neutral, PublicKeyToken=3d22e7ae6a0b3afb' or one of its dependencies. The system cannot find the file specified.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Activities;
using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Workflow;
using Microsoft.Xrm.Sdk.Query;
using Microsoft.Crm.Sdk;
using IBS.MSCRM.Core.Library;


namespace IBS.MSCRM.IBSConstruction
{
    public sealed class FetchXMLReturnConsProjectParticipant : CodeActivity
    {
        [Input("FetchXMLQuery")]
        public InArgument<string> fetchxmlquery { get; set; }

        [Input("FieldName")]
        public InArgument<string> fieldname { get; set; }

        [Output("Result")]
        [ReferenceTarget("ibs6052c_consprojectparticipant")]
        public OutArgument<EntityReference> result { get; set; }


        protected override void Execute(CodeActivityContext context)
        {
            Crud crm = new Crud(context);
            var res = crm.FetchXML(this.fetchxmlquery.Get(context));
            crm.ts.Trace("Query result count: " + res.TotalRecordCount);
            crm.ts.Trace("Query result entity name: " + res.EntityName);
            if (res.Entities.Count > 0)
            {
                //Implement your function here...

                Guid consProjPartID = Guid.Empty;

                Entity consProjPart = (Entity)res.Entities.FirstOrDefault();
                consProjPartID = consProjPart.Id;

                this.result.Set(context, consProjPartID);

                //Implement your function here...
            }
            else
                this.result.Set(context, null);
        }
    }
}