Hi Saurabh,
If you still facing the issue, try this:
Option 1: Remove the EHP1 ESS role and assign /SAPSRM/EMPLOYEE (and similar role in portal) and try. This option activates the Wizard Shopping cart for the employee ( 4 step shopping)
(or )
Option 2: Keep the EHP1 ESS role and activate the "Simplified Shopping Cart" under "IMG-->SRM-->SRM SERVER -->Cross-Application Basic Settings -->Self-Service Procurement --> Activate/Deactivate Simplified Shopping Cart.
This option activates the Simplifies shopping cart for the employee.
Let me know how it goes.
Regards
Venkat