Hi Sravanthi,
I would recommend using the tcode ST01 (*authorization trace) and having user *user1 and recreate the authorization error. That will tell you ALL of the objects checked and whether the user passed or not. The transaction codes related to the authorization objects in PM functional activities failed and it’s stopping the user to post the operation confirmation. You need to find out where its failing.
Other references:
SAP ERP Authorizations for Mobile Users session in SAP WM admin guide.
1892987 - SAP Transaction Code list for Mobile App.
Thanks
Resmi