I am having the same issue. I created a form for a department that has many standard fields that our Providers require. Once the form was completed and published. I copied that form to use it as my template for the other provider forms that need most of those same fields. But now when I click on the variable tab 'For the copied form' It's missing two of the key variables I'm needing. I've tried re-creating those two fields on the form, the variables show up on the form, but not in the Variables Tab or in the service task pane.

This was a a big form and I am not relishing the idea of re-creating it from scratch. :(