Percent complete is not updating correctly on project

[Chahak kindra]

Percent complete is showing 100 % even only one project task is closed complete and all others are in progress.

I have checked business rules and ACLs but still not able to find the issue. Please assist.

[Uncle Rob]

What does the WBS look like?  
Has the project ever been marked as complete, then moved back to open?

[Chahak kindra]

We are using parent child relationship and project has never marked as complete.

[Chahak kindra]

Can someone please assist.