The FormsCentral Desktop app installed with Acroabt XI uses Acrobat to create the PDF form. Because the Acrobat trial expired it won't let you create the PDF even though you have a paid FormsCentral account. Its just a limitation of the Desktop app installed with AXI.
Just go to the web browser and use FormsCentral - https://formscentral.acrobat.com/SignIn.html
If you have a premium account you can create PDF forms without issue. Just make sure all of the forms you have in the Desktop app are moved online, otherwise you won't see them in the web browser.
Sorry for the confusion.