SNC -You are not authorized to use transaction /SCA/ICH_S

Hi All

I am trying to configure Purchase Order Collaboration Scenario of SNC 7.0 . I have assigned the following roles to the supplier internet user

SAP_LIME_USER

SAP_SCM_ICH_SU_SUP

SAP_SMI_EXT_MD_SUPERUSER

SAP_SMI_SUPERUSER

When logged into SNC system using the above internet user. I am not able to open the Supplier WebUI transaction

The following error message is displayed "You are not authorized to use transaction /SCA/ICH_S"

Can anyone guide me what additional roles need to assigned to open the above transaction.

Thanks

Vinod