Workflow Varible Issue

I am using Windchill PDMLink Release 12.0 and Datecode with CPS 12.0.2.4 Windchill Workflow Issue: I created a global workflow process variable and assigned the current task activity comments to it. The value is displayed correctly in the current activity using System.out.println(). However, when I access the same process variable in the next workflow activity, it returns null instead of the expected comment.