Hi Baskar, Thanks for the blog referral.
However, I double checked and my observation is correct - Even though your variables match the values in the variable substitution table, you will still have this error if your variables aren't ALL IN LOWERCASE!
It seems PI automatically converts the variable names to lowercase and expects to find them defined in lowercase in the variable substitution table.
My observations are based on a dual stack PI 7.31 installation.
Once I maintained all variable names in lowercase, everything worked well.