Adding hyperlink to grid gives disabled error

I have added a view (ContractDetails) in a BusinessAccountMaint extension.  One of the columns contains a Vendor Number and I would like to add a hyperlink on that column to make the related vendor number appear in a popup window.  The Vendor Number column is defined as follows, it is just a lookup field.

    #region UsrVendor
    [PXString(15)]
    [PXUIField(DisplayName="Vendor", Enabled=false)]
    [PXDBScalar(typeof(Search2<BAccount.acctCD
     ,InnerJoin<POVendorInventory, On<POVendorInventory.vendorID, Equal<BAccount.bAccountID>>
     ,InnerJoin<ContractItem, On<ContractItem.recurringItemID, Equal<POVendorInventory.inventoryID>>>>
     ,Where<ContractItem.contractItemID, Equal<ContractDetail.contractItemID>>
     >)
    )]

    public virtual string UsrVendor { get; set; }
    public abstract class usrVendor : PX.Data.BQL.BqlString.Field<usrVendor> { }
    #endregion

Here is my code for the hyperlink and popup window. I’ve added ViewVendor in the column’s LinkCommand.

    public PXAction<Vendor> ViewVendor;
    [PXUIField(DisplayName = "", MapEnableRights = PXCacheRights.Select, MapViewRights = PXCacheRights.Select, Enabled = true, Visible = false)]
    [PXEditDetailButton]
    public virtual IEnumerable viewVendor(PXAdapter adapter)
    {


      if (ContractDetails.Current != null)
      {
        ContractDetailExt contractDetailExt = ContractDetails.Current.GetExtension<ContractDetailExt>();

        VendorMaint docgraph = PXGraph.CreateInstance<VendorMaint>();

        docgraph.CurrentVendor.Current = Vendor.UK.Find(docgraph, contractDetailExt.UsrVendor);

        if (docgraph.CurrentVendor.Current != null)
          {
            throw new PXRedirectRequiredException(docgraph, true, "Vendors") { Mode = PXBaseRedirectException.WindowMode.NewWindow };
          }

      }
      return adapter.Get();
    }

However, when I click on the Vendor # I get a message:

Error: The View Vendor button is disabled.

And based on PXTrace messages, none of the code is being run.

What might I be missing?