I have got the same error, looking at the powershell script it is trying to access following URL - http://episervercommercedemo/apps/shell/pages/login.aspx?esso_type=GenerateToken&esso_u=admin&esso_p=store

When testing on the browser, it works fine. Have you managed to fix the issue?

Ok I have figured this out.

Your episever commerece website's application pool needs to be running under .Net 2. It might give you an error -  Could not load file or assembly 'System.IdentityModel.Selectors, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'

Resolve this using steps mentioned here - http://www.david-tec.com/2013/03/Running-an-existing-EPiServer-CMS-6-R2-on-Windows-8/.

Test it worked by going to http://<<YourEPiServerCommerceSite>>/apps/shell/pages/login.aspx?esso_type=GenerateToken&esso_u=admin&esso_p=store

If it returns a security token (and not a login page), the deployment center should not have any problem.

I had compared \eCommerceFramework\5.2\episerverCommerceDemo\Shared\Apps\Shell\Pages\Login.aspx for the project where the commerce manager is working, with episerver commerce installer

The installer downloaded from EPiServer has got following code missing (which explains a lot)

    protected override void OnPreInit(EventArgs e)
    {
        // add P3P header, in order to allow third-party cookies, especially for IE to allow third-party cookies, which will be set through iFrame
        // http://www.p3pwriter.com/LRN_111.asp
        // the compact policy string using here is taken from http://msdn.microsoft.com/en-us/library/ms537341%28v=vs.85%29.aspx
        System.Web.HttpContext.Current.Response.AddHeader("p3p", "CP=\"NOI ADM DEV PSAi COM NAV OUR OTR STP IND DEM\"");
        
        // check if we have EPiServer SSO request, otherwise, process eveything like normal
        if (!String.IsNullOrEmpty(Request["esso_t"]) || !String.IsNullOrEmpty(Request["esso_u"]))
        {
            string redirectType = Request["esso_type"] as string;
            if (redirectType == "GenerateToken") // got generate token request
            {
                Server.Transfer("~/Apps/EPiServerSSO/GenerateToken.aspx");
            }
            else // got SSO login request
            {
                Server.Transfer("~/Apps/EPiServerSSO/Authenticate.aspx");
            }
        }
        else
        {
            base.OnPreInit(e);
        }
    }

Hi Jay

I tested generate the token url, however it just gave me the login page. I could use the default credential to login to the site, but I couldn't use the deployment center to install the Enoteca sample site. I kept receiving the following errors

An unhandled error has occured:
The remote server returned an error: (404) Not Found.
When executing
At C:\Program Files (x86)\EPiServer\CMS\6.1.379.0\Install\Modules\EPiServer Eno
teca 1.1.2.62\Application\ShareLib.ps1:70 char:5
+ $response = $request.GetResponse()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

False
=
Get-EPiIsBulkInstalling
An error has occured and the transaction will be rolled back
Rolledback
At C:\Program Files (x86)\EPiServer\CMS\6.1.379.0\Install\Modules\EPiServer Enoteca 1.1.2.62\Application\ShareLib.ps1:70 char:5
+ $response = $request.GetResponse()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
System.Management.Automation.ParentContainsErrorRecordException: Exception calling "GetResponse" with "0" argument(s): "The remote server returned an error: (404) Not Found."

Any suggestion?