Set external pv error. "An error occurred while trying to update the PVs of process with id 12345: Insufficient permission"

Hi All. 

Am using Set External PV plugin to update process variable of two different process. Lets say process ids 12345 and 54321 and both PM are having same security. But I could able to update PV for process 54321 whereas I couldn't do the same for other process. Its showing below error.

 "An error occurred while trying to update the PVs of process with id 12345: Insufficient permission"

Can anyone suggest how to troubleshoot this?

Thanks in advance!