Make sure you have got correct entries in forms.xml file.
From ENTRIES I mean the form generated thru Advance Tab should have got entry in forms.xml. Do check the value of Task Name attribute as well and make sure it is reflecting the correct task name.
Thanks Anurag for instant reply,
I have manually changed form names and accordingly changed forms.xml,processdefination.xml reflecting my forms get visible.
also i am not sure Should form names be start with form.aaa.xhtml
it does not matter what the name of a form is, as long as it is identical to what is in the forms.xml file