Take the scenario, I have created a portlet DemoPortlet with instance name DemoPortletInstance.
Now I decided to undeploy the DemoPortlet.war file and Again I created one more Portlet with name TestPortlet and here I created the Instance name as DemoPortletInstance. Which is same as above portlet which I already undeployed.

Now what is there on the admin screen. Portlet definition is created correctly but Portlet Instance is not displayed under Portlet Instances tab under Admin tab. Now If I try to create the instance name DemoPortletInstance manually then it is not creating that instance and in logs it says that instance already exists.
But I cann't use that instance in the application.

Please let me know if anyone has faced the same problem and got any solution for the same

I am using jboss-portal-2.7.0.
I tested this problem on Windows and Linux OS.

Thanks,
Vijay