Incomplete Values on Form :(

Just set up a form, and when I go to Submit it says "Incomplete Values" and asks me to Go Back, where it ends up taking me to the front page of the form and wiping all the input data :(

I cloned your form and noticed that the Required option for the Preview Before Submit widget is turned on. This might be why you are getting the "Incomplete Values" error. The widget is required, but there is no way to fulfill its requirement so you get the error upon submission.

To resolve the issue, simply turn off the Required option of the Preview Before Submit Widget.

If you need further assistance, please let us know.
Regards.