Alright - I figured out a trick! When I went to dining reservations and tried to click on "Add you reservation" and then I entered the confirmation # and other information asked, nothing happened and nothing showed up in my reservation list.
However, if you click on "My Disney Experience" up by the shopping cart and then click on "Link Existing Reservations" in the right hand column and enter the information for your dining reservation then it might show up for you. That just worked for me anyway!!
Good luck!