Hi Jagatjyoti,
Do you see any error messages in the stdlogs? Could you paste the update code in this activity for us to validate how it was customized. Ideally "make_required=yes" will enable any filed to mandatory.
Have you tried pdm_webcache in your server and checked the behavior? If needed, Clear the browser cache and open a new browser and test the scenario once again.
Let us know the results.