ebay.shiprush.com integration with shiprush web

[parts_rescue]

I am trying to implement Web Shipping Javascript SDK for the first time. My credentials only work at ebay.shiprush.com and not my.shiprush.com.

This is my code:
In webpage:

<link href="https://ebay.shiprush.com/static.shiprush.com/ship.app/api/webshipping.integration.client.css" rel='stylesheet' type='text/css' />
<script src="https://ebay.shiprush.com/static.shiprush.com/ship.app/api/webshipping.integration.client.js"></script>

js:

function openShipRush(){
    let shipment = {
        ShipTo : {
            Name: 'John Doe',
            Address1: '1 Main St',
            City: 'Cincinnati',
            State: 'OH',
            PostalCode: '45140',
            Country: 'US',
            Phone: '5131234567'
        },
        CarrierTypeName: "USPS",
        ServiceTypeName: "USPSPriority",  
        Packages: [{
            Weight: 1, 
            WeightOunces: 0, 
            Length: 4,
            Width: 4,
            Height: 4
        }]
    };

shipRushClient.Open(
    {
        //MyShipRushWebsite: 'ebay.shiprush.com',
        Shipment: shipment,
        OnShipmentCompleted: function (data) {
            alert(data.Shipment.TrackingNumber);
            // Return "true" to close shipping form
            return true;
        }
    });

If I don't include MyShipRushWebsite: 'ebay.shiprush.com' in js and I log into ebay.shiprush.com before clicking button to trigger shipRushClient.Open, the shiprush web client works as expected. However, if I am not logged in to ebay.shiprush.com ahead of time, js will launch my.shiprush.com login. My eBay credentials do not work there. I thought I could resolve that by adding MyShipRushWebsite: 'ebay.shiprush.com' as shown in the code above. However, when I add that I get an error. In the console I see that my web application is trying to launch https://mywebsite.com/ebay.shiprush....adShipmentView. Note: Mywebsite is the URL of my web application that is trying to launch the shiprush web plugin. I believe that I need it to go to https://ebay.shiprush.com/ShipButton...adShipmentView, right?

Is this a CORS problem? Is CORS configured differently on my.shiprush.com than it is on ebay.shiprush.com? How can I get my Javascript to launch the ebay.shiprush.com login rather than my.shiprush.com?

[SYSOPS]

We've opened Case 70986 to review this further. Currently there isn't a control in the shipRushClient.Open call.

Thank you,
SYSOPS