Page not found error on portal

Hi Experts,

I am a facing an issue on portal where when I am trying to create a shopping cart through portal via Purchasing role and try to add item and select the custom item, it gives me the below error.  We are using the standard SRM role for operational purchasing. System connection is set up on portal and SAP_SRM alias is also set up.

Screenshot of standard role

Moment after I select the item , i get the error. Please suggest.

Thanks