What does your rule look like now?

What kind of dropdown are you using? Maybe the internal value isn't "Approved" - you can check this by adding a calculated control on the form and display the current value of the dropdown in there.

Your rule should look like this, if the value really is "Approved".

Thanks for your reply Jan, I was complicating the things as my dropdown was in repeating control.Instead of checking {Self} I was checking the  control property